There are a bunch of historically grown issues with current Toolbar/Tools layout/code (in no logical order and mostly caring about WikimediaUI theme here):
[x] {T176106}
[x] Minimize action button selector output – https://gerrit.wikimedia.org/r/#/c/381800/1
[x] Remove `box-shadow` from active tool-items not in design – https://gerrit.wikimedia.org/r/#/c/381628/1
[x] Fix `border` on narrow bottom toolbars overflow – https://gerrit.wikimedia.org/r/#/c/381802/1
[x] PopupToolGroup header is a feature, but neither in demos nor styled – https://gerrit.wikimedia.org/r/#/c/381801/
[x] Highlights (`background-color`) of active tools and toolbar menus should be equal – T177278
[x] Opacity of active, flagged icons is wrong – https://gerrit.wikimedia.org/r/#/c/382077/
[] Turn more/fewer arrow in more/fewer tool in bottom positioned toolbar
[] `position: relative` to Toolgroup.less in general
[x] Accelerator keys' `padding` should be handled per theme, not in theme-independent PopupToolGroup – https://gerrit.wikimedia.org/r/#/c/382090/
[] Tools and menus focus should be aligned with other widgets
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Some more descriptive images:
| Before | After
| -- | --
| Border on narrow bottom toolbars | -
| {F9963542 width=50%} | {F9963549 width=50%}
| PopupToolGroup header | -
| {F9963531 width=50%} | {F9963534 width=50%}
| Highlights active elements | -
| {F9970928 width=50%} | {F9970932 width=50%}
| Opacity of active, flagged icons | -
| {F9987479 width=50%} | {F9987481 width=50%}
| Accelerator keys padding | -
| {F9988157 width=50%} | {F9988162 width=50%}