WIP: resolving GNOME/gnome-todo#129. Got stuck. Need help.

I've been working on this for a while now. Need some help with this. Also, after that is solved, I don't know how to deal with GUI and open specific panel. I've been digging about it and found functions that deal with GUI, but still can't connect all the dots. I'd be glad if someone could point me in right direction. Thanks!