Hi,
I created a branch "command-manager" where I put a draft of the command manager I am working on. I added a dependency to gmodule in order to get the glade UI connected to C callbacks. It is great, it only takes a few lines of code to get things work. I tested it on Gtk2 and Gtk3 and it seems to work, but I'd like some more checks.
Could you please run denemo, then Edit > Customize… > Manage Command Set and check that you correctly see the new interface. Then, click on a button on the top bar and check that something is displayed in the console.