I cannot reliably trigger this behaviour, so this is just a heads-up or request to keep eyes open for.
DT 3.7.2 (but certainly also occurred in 3.7.1), macOS 11.3.1, Intel iMac. DT is set up with a Navigate/as List/Standard view configuration. Databases, inboxes, tags are unified. Automatically expand & collapse is set.
In the sidebar, I double-clicked a database to display its contents in the sidebar. Then I selected a group in that database from the sidebar; the contents of the group were then displayed in the view area as list. I scrolled down the list, opened an item by double-clicking; the item was opened externally in Preview. When I now returned to the DT main window by clicking somewhere (and no, I’m not completely sure where; certainly not in the sidebar below the current selection, as that area was covered), the view area still shows the contents of the group previously selected from the sidebar but in the sidebar the grey selector highlight is on the name of a different database. I have also previously experienced the selector highlight on the name of a smart rule - again, whilst still displaying the contents of the group previously selected.
I cannot trigger this; if I intentionally select a different group/database/rule in the sidebar, its contents will invariably be displayed in the view area.
It seems as though there is some condition which can cause the “optical” selector highlight in the sidebar to jump (always down, never up in my experience to date) without actually moving the focus of the selector highlight.
I will report back if I find any kind of consistency to the behaviour.