I had hoped, someone else has an idea, but obviously not.
From the mapkey I can only see that the file is saved with no name specified, so the default name would be used.
I guess if you break up the mapkey after the Save As command, before the OK, then maybe you will be back in control to enter the name - of course you will have to complete the action then.
You may give it a try with the last two lines replaced by this remains of the next to last line:
mapkey(continued) ~ Activate `post_proc_opt` `Output`;