I'm testing on freshly installed out of the box portable 8.9.0. Prior to installing CCR I changed L&F Main interface to: small toolbar icons and two line tool bar labels.
Keyboard shortcuts is much better, now that all those pesky "None"s can be hidden.
- Would it possible to show the default settings as a separate column, i.e. Assigned and Default.
- If I double-click a CCR shortcut item the Shortcut editor pops, if I change any shortcuts when I return to CCR its shortcut list is not refreshed… IMO it should be.
- If I press Enter on a CCR shortcut, it pops a Windows File Explorer window for the location from which I started calibre-portable… IMO it should do the same as double-click. Other panels are the same… actually it's worser, if I press Enter anywhere - even Help this FX window pops.

Still not seeing borders on the inactive tabs, do you have any Qt qss properties set or a customised colour scheme.
If an item on a list has focus the hardcoded Ctrl+Tab and Ctrl+Shift+Tab do not work. IMO they shouldn't be hard coded.
CCR History reports CCR reinstalled every time I invoke it:
BR