If I have one bend in a part, I will use the flat command. Then, as I am designing I realize that I want to add another bend along the edge next to it. The way that the corners interact is not good if you simply add another flat. I want to use the flange commmand. Unfortunately to do this, I have to delete my flat, and recreate to whole thing using the flange command. We are always, in my case, dealing with sheet metal part bent in a brake press, so no curved flanges.
There are three ways that are possible to fix this.
1. the best way would be to allow the cntrl click to add edges to a flat. You could have the options that you need for corners treatments greyed out until you have more than one edge selected.
2. create a command to transform a flat to a flange so that you could add more edges to a part. I could see this having more issues becuase of the different types of flanges vs flats. In the sheet metal industry, I think most of the time a simple bend is being used.
3. make it so that the flats interact with each other to create geometry that makes sense (like in the flange command) either automatically or with a another feature.