If you drag program to a free space on button bar you can just drag it without pressing any additional keys (but you can freely press Shift or Ctrl if you want

, this won't harm).
If you want to create new button between existing buttons you should press Shift while dropping.
Am I right? (I admit that my PC could be special after the story with my TC command line and Explorer behaviour...)
EDITED: Sorry! I haven't noticed that this thread is for
pocket TC... Don't know anything about it, so I may be wrong...