And yes, I forgot to mention, that what you were trying to do with subpart is not possible (unless you want to use a dummy subpart) but can definitely be done with connection but you will need to handle the subpart creation (using your own button and corresponding code).
Yes, I'm sure. Verified few times.
I have 2 grids on a UI step. One of them is mapped to the UIVoltages subpart collection the other one - to the UIVoltagesDisplay. The grids behave the same..
This is really odd - never seen this behavior. The grid context menu has always followed the user edit setting (if it was tied to a subpart) and disabled if it was tied to a connection. The next logical thing to do (you might have already tried it) is to see what happens when you click the 'add' while it is tied to a connection. Does it actually create a brand new part (under which subpart) and add it to a connection?