I would listen to Jorge Castro :) But since I dont and like to tinker around... Ive only ever had one problem with Ubuntu Tweak and that was early on when the program first came out. It deleted something in the OS that wasnt supposed to be deleted and I was having all sorts of errors.
A year or two later now, its one of the first programs I install on my own system. I also do all the cleanup stuff and have not had a problem (minus that one time). For tinkering Ubuntu users, Id install it... for regular users or if you installed Ubuntu for a friend, they will never really need it.
Ubuntu Tweak only offers (currently) a limited API call for the executable itself.
Therefore - when trying to invoke a Ubuntu-Tweak feature when starting from startup applications or via a quick list, you can only use the command line parameters that have been made available.
ubuntu-tweak -f janitor is one such feature. There are no command-line parameters (currently) for what you are seeking to do.
You can test this yourself by running ubuntu-tweak -h. The linked answer above shows the typical result you could expect.
Some programs - once running - expose an interface such as dbus that allows you to invoke features via an external program. Rhythmbox is one such software with its rhythmbox-client which can be called externally. Ubuntu-tweak unfortunately does not offer the same external interface.
What you'll need to do is submit a patch to the author that would add a command-line parameter to do the function you are seeking.
Alternatively - add an externally callable interface such as dbus when ubuntu-tweak is actually running.