These are my shortcuts for Main window layout
My standard layout is to have Book details under the Book list and Tab browser hidden.
Whilst exploring this issue
Display error in Calibre 7.3 I made use the the shortcuts to force a horizontal scroll bar.
When I pressed Ctrl+Alt+T the Tab browser appeared

, then, when I pressed Ctrl+Alt+L the Book details moved from under the book list to the right edge

… and the Tab Browser disappeared

.
If I press Ctrl+Alt+L again the TB reappears

.
If I swap the key presses to Ctrl+Alt+L and Ctrl+Alt+T it's okay, but when I press Ctrl+L again the Tab browser disappears too.
The tooltip for some of the status bar buttons are erroneous (could be, they've been ever thus), viz:
Layout action toolbar item has some issues too:
It doesn't show the shortcuts, most other toolbar items do show them. IMO it should have an action to set the BD position (bottom edge or right edge) and, to make it consistent with the status bar buttons, a Quickview hide/show.
BR