As a suggestion, it would be MUCH easier if you could see the performance you are working on while you are trying to add rigs to it. And a drag and drop interface so you could see what rig you are adding to a specific performance slot would be SOOO much faster.
Or, did I miss this feature somehow and didn't know it?
OK, I admit it, I didn't read the Rig Manager manual, so if there's already a drag and drop and I missed, my apologies.
Right click and select Open In New Window
you will now have one instance of RM open in the Performance view and a separate window (which can be dragged and resized as necessary - I use two screens with one on each screen) with the browser pool of rigs.
now drag a rig from one window and drop it in the desired performance slot in the other window.