Thank you for the feedback.

Your suggestion is very similar to this one, so I'm closing it as a duplicate:

https://tweaker.userecho.com/topics/476-notification-area-on-all-displays-multiple-system-trays

Please see my answer in the topic above.

Thank you, I closed the other topic.

Thank you for the report. Closed as a duplicate of:

https://tweaker.userecho.com/topics/14-windows-10-remove-clock-padding-on-vertical-taskbar

Also, you can use the tweaker option to show desktop by double-clicking or middle-clicking the taskbar. You can also use the "Reserve empty space on taskbar" option to always have a space to double/middle click. Refer to the help file for more information.

What kind of lag?

Regarding the vertical lines, you can lock the taskbar by right-clicking on it and choosing the Lock option.

You should be able to do that:

https://www.howtogeek.com/howto/28600/move-the-show-desktop-icon-to-quick-launch-or-taskbar-in-windows-7/

Thank you for the support, I appreciate it!

Actually, that have been possible at least since 2011 :)

Right, makes sense.
Combining options weren't designed to work with the "Combine when taskbar is full" configuration.

With "Combine when taskbar is full", Windows decides when to combine/decombine groups, according to the available free space, and so the tweaker options for combining have no effect.

I can think of only one explanation: perhaps you changed Firefox to specifically not combine.

1. If you right click on Firefox's AppId (here), are there any configured settings?
2. If you open multiple windows of a different app (say, Notepad), do you still see multiple items?