If you have a hard drive, or floppies with very large directory trees, it canbe very irritating to use *Dir commands with very long pathnames. This is where !SetDIR comes in.
If you drag a directory to the icon on the iconbar, then that directory will become the Currently Selected Directory (CSD). Eg: if you press F12 and type *. then the contents of that directory will appear.
This is nothing new however, because there must be hundreds of applications which do this in the Public Domain. But !SetDIR has another feature: On the iconbar menu you will see the entry: 'Cr Obey'. If you select this, then when you drag a directory onto the icon, not only will the directory be made the CSD, but an Obey file will be created inside the directory, which when double-clicked executes the *Dir command with the full pathname of the directory.
Repeatedly selecting 'Cr Obey' toggles this facility on and off.