-- Through experimenting, the Song Information Editor (and underlying My SQL tables) will let me define new one-character "Types", such as U-Uptempo, or B-Music bed. Could the scroll window in the GUI be "taught" to incorporate those new items in its pick-list or at least allow me to enter it?
As far as I know, only those songtypes that are predefined will be available in Search and Group display.
The songtype field is just a single letter field, so in theory there could be up to 26 different types, but SAM isn't meant to use the "undefined" ones.
Perhaps related, I'd also benefit from a simple *display* (even of not searchable) of songs genre and/or type in the playlist window, if only to help a live announcer know the kind of element that is about to emerge from the list. I'd even be willing to work from MySQL to do this is it's feasible to create a variation like this. Any thoughts there? Thank you.
In SAM 2019, you can use junction points or symlinks for organizing your categories/genres/whatever on your harddisk and browse that via the File manager of SAM 2019.
That's the end of where you can get within the SAM-UI. (At least for your purposes. There are a few Dialog options in PAL, but none of that is anywhere close to table listings)
If you're willing to use external tools like the webbrowser or custom-built-graphical-user-interface-software, you can pretty much manage anything (except for the actual playback decks) through the database and filesystem. That includes searching and controlling playlists/queue/requests.
None of that is built-into SAM or available out-of-the-box, though. You can either learn a programming language and an SQL dialect (preferrably MySQL or IBSQL for Firebird) or hire someone to build custom software for you.