IN Tools > Options > File Options > Backup: Exclusions.
Set exclusions to something.
OK
Go back and try to clear the field.
Slick won't let you set it empty - it keeps putting back the previous value.
Also, give some hint as to what it allows as exclusions.
I tried ANT style paths - and apparently that isn't recognized, but I could only tell thru experimentation to see what was or was not being backed up.
Exclusions should allow more than a single directory name.
It should accept filename patterns at least, like: *.obj;*.exe, etc.