Why would you want RetroFE to launch Notepad to edit a batch file? Are you trying to RUN a batch file?
If so, create a launcher that looks like this:
executable = C:\Windows\System32\cmd.exe
arguments = /C "%ITEM_FILEPATH%"
and in the settings.conf in your collection, point to said launcher and make sure your list.extensions looks like this:
list.extensions = bat
I'm doing this to run my DOSBox games in RetroFE and am using batch files due to the unique constraints of the majority of games in the collection.