Some feedback:
Signup process is tedious. I have to create an account to even see how it works. I have to pick a username AND give an email address. I have to validate email address with multiple clicks (click link then click button on loaded page). Then I have to reenter everything to sign in.
First view of the system says to click and drag links to reorder them. Clicking and dragging links does nothing until you enter edit mode. I almost gave up assuming the thing didn't work at all before I discovered this.
No "Save" button in edit mode. Just close edit mode... but this doesn't allow NOT saving, which is somewhat unexpected since it's a separate mode.
Visiting a new page seems to automatically put you in edit mode, which persists when visiting other pages. Honestly, I'm not sure at this point why I would ever not want to be in edit mode. I suggest getting rid of modes and providing an undo to roll back any accidental changes.
Number of groups shown across width should be dynamic based on window size not fixed.