Documentation: Tracked changes in Google Docs?

Yes. It's called suggestions. Share with Edit permissions. Uncheck the email notifications. Much like MS  Office, comments also exist in Google Docs as well as a Compare option in tools and a revision history (with human readable names that can be set by the user):
https://www.pcmag.com/article/330137/tip-how-to-use-track-changes-in-google-docs

Missing TBC: The Combine (with generated inline tracked changes) option, much useful to know what words changed between 2 revisions when someone forgot (or "forgot") to start tracking changes. If you have PDF versions attempt a conversion of PDF to docx and then combine (Office does it).

Documentation IS part of the configuration of a software so, do learn to use productivity tools. This is why it's called productivity tools.

TOOLS. Ditto clipboard manager (productivity tools; multi-PC)

Yest another free clipboard manager (see the ARS Clip link here)?
http://ditto-cp.sourceforge.net/

Quoting:

Ditto is an extension to the standard windows clipboard. It saves each item placed on the clipboard allowing you access to any of those items at a later time. Ditto allows you to save any type of information that can be put on the clipboard, text, images, html, custom formats, ...

Interesting features:

• Keep multiple computer's clipboards in sync (encrypted)
• It has a portable installer.

TBC: how does it stack against ARS Clip?

TOOLS: NewFileGo (productivity tools - File watcher task runner)

From the same supplier of ARS Clip (Clipboard Manager), the NewFileGo is another important productivity enhancer, allowing you to perform a task every time a file appears on a certain location.
For repetitive tasks it's the dream of everyone.

NewFileGo can be downloaded here:
http://www.joejoesoft.com/vcms/170/

FFR

TOOLS: ARS Clip cliboard manager (productivity tools)

ARS clip is THE free, open source (mainly windows-based) clipboard manager: http://www.joejoesoft.com/vcms/97/

Quoting:

ArsClip is a freeware "clipboard manager" utility. ArsClip monitors the clipboard and keeps track of the entries. Pasting is done by using a triggered popup window. This window can be triggered by a hotkey, holding right-click, a special trigger window, and other methods.

ArsClip used to be barebones, but I think I can safely say that it has become a nicely featured and highly configurable program, due to user feedback. The program now specializes in copy-and-paste automation tasks.

Delphi XE2 source code included

Features

- Permanent Clips/Macros for copying and pasting automation 

- Picture, RichText, File Copy, Unicode, HTML support

- Highly configurable

- Win7 Jumplist support

- Optional Clipboard Bar -- clipboard viewer

- Optional Global Clipboard to shares clips with other Windows and Android devices 

Requirements

This program requires no installation, but an optional setup program is included. Supported on Windows XP through Windows 10.

Interesting features include:
- Shortcut to recent items as a context menu (Ctrl+Shift+Z)
- Permanent items
- Persistence between restarts
- Stripped down format paste (Ctrl+Shift+V)
- The global shared clipboard (not yet tested by me)

Cons:
- Some minor issues: Slight instability (Windows 8), initial error setting global keyboard hook and some minor problems with OneNote (copied values are always pasted as image in certain apps).

PS. Also from the same supplier, make sure to check a very interesting tool for automating file-based tasks. If you like it, think about making a donation.

TBC: How does is stack against Ditto?

TOOLS: Time trackers - What are they and what are they good for (if anything)?

When doing software development it could be useful to track your time (split task types into categories) and start counting. Utilities with a start-stop interface are the less intrusive ones for this purpose.

We all know there's a difference between a plan and real-life execution (project plans, life plans, etc.). This is also valid for our daily plan (we do plan every day right?). If we do track time spent on our daily tasks most of us will for sure be surprised how differently we spend our time (when compared to our initial plan). In software engineering, for your projects, Project Monitoring and Control, helps us keeping projects (and its plans) on track. What about in your life? The % of effective time spent working sometimes is radically different from our first mental guess (and maybe this is why time runs out without things getting done: because we are NOT doing it).

But we mustn't panic: Typically it is normal that we don't spend 100% of the time working but do you know your %? This is because there are context changes as well as several types of interruptions including meetings, phone calls and many other asynchronous events that will make you stop te current task (and incur into new context changes). Also, this is why we should never plan 100% of our time fully.

Repeating the question: Do you know the average % of  time you are able to be productive?
If not, try using a time tracker for a week, so that you have the numbers. There are for sure published studies on this productivity topic (google is your friend) but only after having your own % number you can start thinking in optimizing the way you spend your day (you can only optimize what you can measure).

Some example of time trackers are listed in this article (mini-review):
http://www.makeuseof.com/tag/6-free-and-useful-desktop-based-time-tracking-software/

My minimum requirements for such a tool are:
- that's in your budget (mine is zero, so I look for freeware)
- that allows you to define task categories (don't try to track individual tasks, unless you really need to); things like, analysis, coding, testing, meetings, [coffee] break (if you're doing SW development);
- that has a start/stop interface (a plus would be to pause tracking time when the screen saver enters in action - I don't know many people that are able to work while the screen saver is running)
- that presents you some reporting on the collected data (charts, dashboards - per day, week, month)
- that exports data to CSV/XLS format (for further analysis, if needed)
You could have additional requirements, e.g. "has a web interface" but for me this is not required.

PS. For personal productivity tips (not properly related to tools) you could try these:
http://umdiadestesvou.blogspot.pt/2016/09/um-dia-destes-vou-testar-mais-dicas-de.html

TOOLS: Intermission: Mouse without borders

In this intermission I give you: "Mouse without borders". To be more exact it's Microsoft that gives you the utility for free here:

https://www.microsoft.com/en-us/download/details.aspx?id=35460

Grab it while you can (not that I believe that it will stop being free).

To Install and Configure it

You only need to download the utility on 2 computers, run (your favorite AV and then run) the setup; use the host name and software-generated key (that you'll have to write down in the second computer); after that the master computer performs a quick location config (so that "the mouse knows where to go").

What's it good for?

This is a productivity tool that allows you sharing a same mouse (and keyboard) in several computers without having to be switching between those hardware devices.
You just need to say where the other computers are (physically, in relation to the "master computer") and the mouse will move there (without borders). The tool will allow you also to copy text (and files!) easily between (up to) 4 computers. 

It's useful for some of these scenarios: 

- Testing (if you record results on a system and you need to test interactively on another). Grab text from that error on one place and paste it on the place you have the test management tool. Precious time saving.

- Programming: when you need to deploy files on servers or other Windows boxes.

- Whenever you have 2 PCs on your desk and you need to frequently change from one to another.

- (fill in your scenarios here). 

AOB

Another tool that works well is Synergy (and this is cross-platform).

(2016-04-21: Rephrases; added cross platform info)