Copy the devo.fs file from your F7 to disk and
extract
the devo.fs file with
buildfs.exe
and edit the 1st line of the tx.ini. Then create the new devo.fs file and copy it onto your F7. I hope there is already a valid devo.fs file on your tx. Otherwise it might be the solution to copy the pristine devo.fs file of the firmware archive onto your F7. When you create a devo.fs don't forget to add the protocols you need like DSMX, J6 Pro, WK2XXX, PPM or USBHID. If you modded your tx with a 4in1 RF module you might also use FHSS protocols (not only DSSS).
Keep in mind that the max. size is 64kb and you need some space for model.ini files too.
Good luck.