Maybe I didn't do the right search, but this should be easy and it's not.

I have a sheet metal part in an assembly.  I want to replace that part with another part, in this case a sheet metal assembly that is almost identical, but that has a stiffener added (two part assembly)   The new assembly has two configurations (std and mirrored).

I have the new replacement assembly open in another window, and in the right configuration.

In my main assembly I highlight the part in the tree, then go to File/Replace (not in my right click selection for some reason)

I have the "manually select" button selected

I select the "with this one" part, as it's already open and shows up in the window.

The first mate that comes up to be fixed is the flat pattern of one of the sheet metal parts.

Ok, something's wrong, so I select the 'X' at the top right to cancel.

But the replace has already happened, so I guess you can't back out of it.  You also can't choose the back loop arrow to reverse this, so I have to dump out of the assembly.

So, questions:

1 How to add the replace command to my right click?

2 How to choose the configuration of the part that will be replacing the existing part?

3 What the heck is going on with the flat pattern coming up?

4 How to cancel the replace