In iMatch 2021, if a folder had other missing child folders, you could remove them by updating the parent folder. That doesn't seem to be possible in 2023.9. A bug or a new concept that I don't know yet?
Bug.
This is caused by an optimization I've added on August. 6. 2023. This change allows the background update queue to continue processing when folders are rescanned, until some actual changes are discovered that need to be processed.
Since IMatch rescans folders often without finding any relevant change (Windows sends many messages to IMatch about "changes" in folders) this allows for a much smoother background processing.
The feature that checks for no longer existing folders and files and removes them was no longer triggered if the parent folder of a folder does not indicate any changes. In case of a forced update, the removal should be run, whether there are actual changes or not. I have fixed this for the next release.
In the mean while, please use the "Remove Folder from Database" command available in folder context menus when you remove folders indexed by IMatch in other applications.