@alex (Original poster)
Sorry for the delay.
Currently, to search for a file in a directory D and all its subdirectories, you can do this:
1) create a new tabble, called for example “temp”.
2) tag the directory D with tag “temp”. In the dialog, choose “tag the folder and all its files”. This will tag all files in all subdirectories of D, recursively.
3) open tabble “temp”.
4) type something in the textbox. This will search among all files in D and all its subdirectories.
you can then optionally delete tabble “temp”.