So far my process (as I've only done this once) was to shut down LibreELEC/KODI gracefully using the menu options in KODI, unplug the USB and attach it to a laptop I bring with me, add/remove/update files as needed, then re-attach and turn the RPi5 back on. I noted that KODI did not see the removed/added files, so I had to have it rescan the library (I don't recall the exact term used in KODI, apologies for that).
I added the 14TB drive as a movie source (all files in one folder, not separate folders) and a TV source (these are in separate folders by program/series). As mentioned above, I use MediaElch to pre-populate the metadata for all the files given the lack of a network.
TL;dr: I'm trying to avoid bringing the laptop to do these updates, I'll investigate the File Manager, I suspect I'll need the keyboard for the best experience with that. Hopefully if all the content is in one folder it'll just let me select all and go.
As far as I know, KODI/LE shutdown and startup are not necessary, it's all plug&play for USB devices. But after adding new files (even if tagged) library rescan is obviously necessary.
You're trying not to use the laptop, correct? So, are you connecting the BD reader/writer to the Raspy, right?
If so, yes I think you'd need a keyboard and a mouse (if you get'em bluetooth it's all ready... just connect them in the LE bluetooth panel and everything will work). I don't go for this straightest option because I don't feel comfortable working with keyboard and mouse in my living room on the couch watching the TV (even with a 50").