I played around with this a little and you’re correct that with the right sequence of events it adds back slashes to the back slashes. I don’t think this should have caused a problem though.
If you create the concat action and save it with the .b separator, it will write \.b\ into the file. Then if you load it you’ll have \.b\ in the separator field. When I saved it again is still only wrote out \.b\ again (I was afraid it might write \\.b\\ but it didn’t).
The reason that it adds extra back slashes in the first place is that the action is evaluated in a TCL procedure and the back slashes by them selves would be escape characters instead of literal back slashes. The xlate GUI is just anticipating this and adding the extra back slashes.
