Your comments

Oh! I see now. Thanks for a thorough explanation. So, dragging buttons outside the taskbar is working for me great. Out of curiosity, is there a way to launch any app instances in a "random" groups by default? Although I'm already satisfied with the drag feature.
Is your goal to have these custom groups (e.g. Calculator + Notepad) temporarily
Yes! Here's a demo:

http://i.imgur.com/tGnX4Vq.gif
Creating new windows messes up my already created groups (new windows get included in existing groups by default).

If it's the former, I don't understand your statement about having to "exclude" every application
I thought excluding an app in the Taskbar Inspector prevents the app from automatically grouping by similarity and allows only manual grouping, but apparently it disables grouping completely for that app (including Shift+Right-mouse-button-drag one).
No-no-no, I'm taking about the ability to group different apps (with different IDs). For example, I'd like to be able to manually group a specific Notepad window with a certain instance of a Calculator. And then another Notepad with another Calculator. But I don't want new windows of a Notepad or a Calculator to be attached to neither of already existing groups. (I would group them when I need.)
> Also, iIt would be great to have an option to disable automatic grouping (by app ID's), allowing only manual grouping.

That's already possible with Taskbar Inspector
Yeah, but now you have to manually "exclude" every application on your computer to prevent them from grouping. And you'll have to keep updating that exclusion list all the time. It'd be cool if there were some kind of wildcard functionality or a switch available.
The option to restore all items of a group is available for testing in v4.5.10.6 beta
Wow! Damn that was fast! Thank you so much!



http://i.imgur.com/YyBKCth.gif
>> There is an advanced option to minimize all windows of a group
> Which one is it?

It's 9, as specified in the help file.
Oh, sorry. I don't know how I overlooked that. That's great news!

Another possibility is to restore all windows, even if some were already minimized
That's precisely what I've been talking about.

If you have the taskbar set to combine [...] you can right click you can choose to "Restore all windows"
That's definitely an option. But I loose the ability to regroup (not reorder, but regroup) my taskbar buttons in "combine" mode :( I still can reorder via thumbnails.

Also, iIt would be great to have an option to disable automatic grouping (by app ID's), allowing only manual grouping.
> There is an advanced option to minimize all windows of a group

Which one is it?

To clarify myself, there's an option called "Left click on combined item -> Cycle through windows" which brings to front every grouped window one by one if you repeatedly click a taskbar combo group button. It doesn't matter if those grouped windows were previously in minimized or non-minimized state. It simply shows the windows regardless of their state. So I'm not sure what 7TT would have to remember, though.

Anyways, 7TT is an amazing piece of work. We just always want more :)