UI Improvements: Dark mode separator visibility improvement | Button Order | Category Tabs

[silversword411]

This has been on my mind for years, finally getting around to improving.

Feedback pls! I've tested on windows, mac/linux testing needed
https://github.com/silversword411/naps2/tree/UI-Toolbar-improvements

First Commit : Fix dark mode divider visibility

Second commit: Rearrange buttons to logical workflow order

Third Commit: Add Category tabs for differentiating workflow processes.

If all is well I'll do a PR

[silversword411]

Are there other changes I need to make for the other OS versions?