Can't switch libraries

[rosehoneywine]

I'm completely missing the option to toggle between Calibre libraries, even though this is something I've done before.

Here's what's going on:

1. I was viewing Library A, and created Library B.
2. I imported a Calibre backup from Sept 2022, plus its settings/plugins, to Library B
3. When clicking the arrow next to the Choose Library button as normal, there is an option to "Switch/create library", but clicking it only prompts me to create a new library. The only other options are to change the icon, pick a random book, apply a virtual library, import/export, and library maintenance. But no option for going back to Library A, or even changing its name/deleting it.
4. I uninstalled Calibre and deleted the entire folder for Library B. But after relaunching the fresh install, the Library B folder is automatically replaced in my file explorer, just empty, and there's still no sign of Library A.

I have Library A backed up and could technically just import it the way it is, but I don't understand what I'm missing here.