Hmm, looks like what I need, thanks!

However, I tried doing that on my phone, but the options for adding new option groups was disabled (there was a menu, it's just that all the entries were greyed). I didn't find anything in the top-level options either.

The web interface has even less options, so I'll probably have to install a desktop version and then sync with my phone - when I'm not at work.

[edit] By the way, I got this to work fine with the latest desktop version. Thanks!