So, once you start creating a few smart lists/folders, it can get a little messy..

I think a nice feature would be the option to have an "Expand/Collapse all" at the top of the Library tab, maybe netx to the "Prev/Next" buttons.

A context menu would also be good to act only on subfolders of the selected folder..

if any of that makes sense....

Yes..definitely makes sense..

Also included should be an "Export all lists" function to export all the lists in one go..

I would like it if CR "remembered" collapsed groups.

On the library tab, when a grouping is selected (e.g. when comics are grouped by "File Directory"), the groups can be expanded or collapsed by clicking the arrows. Groups are expanded by default, and CR does not store whether a grouping has been collapsed (hidden from view). The result is that running "Scan eComic folders" expands every group. Restarting CR also expands every group (rather, it just disregards that I may have collapsed any of my ecomic groupings).

Additionally, to reiterate the OP, a pair of buttons to expand/collapse all groups in the library would also be useful.

Side note: I haven't fooled around with saving workspaces/lists enough to understand how they work. But I have tried to save/restart/reload these to no affect regarding the status of collapsed groups in the library.