I added a Preferences button with the following options:
Private Browsing: URLs are hidden, tapping a tab toggles hiding of the current loaded page in that tab, no automatically launched tab group on next launch of Tabulous
Save Changes on Exit: Automatically saves changes to the currently loaded tab group when the app exits. This will NOT save anything if you Create New Tab Group, then start creating tabs, then exit the app without first saving the tab group with a name. This is intentional for privacy reasons. It allows you to just surf without committing anything permanently, or having these tabs show up next time you launch. You have to explicitly save the tab group the first time.
Also, if you change an existing tab group, you will prompted to save those changes if you try to load a new tab group, clear the tabs, or launch a URL in Safari.
This will probably be the last update for a few weeks. I want to do a code review, and some refactoring as well as trying to decide where to go from here.
Enjoy the update!