P: Removing a photos folder that is not empty but appears empty in the catalog

I realize that LrC folder panel is not a file manager. But in a way it is. It provides the tools to move and rename photo files in your directory structure. Keep in mind, I'm making a suggestion. LrC provides the Remove to remove folders from the catalog, which does delete the folder in the OS if its empty. I'm suggesting they add the decency to alert you when it detects other files in the folder and that it therefore won't be deleted. I do use LrC Remove to clean up folders in both the catalog and the OS. It was only recently that I learned that it doesn't remove non-empty folders from the OS file system... that's after many years of using LR. I have relied on it to remove those empty folders after I moved photos out of them into another folder and renaming folders. Imagine if the two operations were completely disconnected and you had to go into the Finder (on Mac) or Explorer (on Win) and rename folders there and shift the photos around there after doing so in the catalog? you'd stop using LR most likely. It's a convenience to take care of both actions in one exercise. I'm just saying, go the next step and communicate with the user when it can't/won't delete the folder you removed from the catalog and here's why. Offering followup actions upon encountering this situation goes even further in making it a convenience. That's what LR is largely about, making photo management quick and efficient.

Just a thought to expand on what GoldingD posted.

Lightroom Classic only recognizes specific file types mainly photos and videos, if there are other file types in the folder that LrC does not recognize they will remain in the folder. Lightroom Classic will not delete the folder when you select “remove” in LrC.
You will have to use your operating system to identify the remaining files and delete or move them, files could be any file type e.g. word document or even orphaned sidecar files from other raw processing applications.

It is not that LrC thinks the folder is empty, it is that LrC thinks none of the photos have been imported into LrC. The folders panel is not a file manager. The folders panel does not show you the entirety of what is on your computer, just what is in the database that is the catalog.

Mis-read the suggestion. Deleted my response.