I note that in the John Melas Performance Editor is a button marked Auto Set Names that applies an abbreviated label to every Assignable knob that's used, so I can see at a glance what each controller affects. It seems that on the MODX itself, that can be done only manually by tediously typing them in. Is that correct?
Knob names are changed manually or by SysEx.
The tool is likely just modifying the SysEx bulk dump of the performance to change the knob name.
Not that you ask but just FYI for others that may want to know but in order to change the name yourself you would have to:
1. load the performance into the edit buffer
2. send 16 SysEx commands encoded with the name you want to use
P.213 of the data doc shows the table data that holds the 16 characters for knobs 1 and 2 - the three byte address is 37 0p 00 for the 1st character of knob 1's name, 37 0p 01 for the 2nd character and so on.
p.188 shows the format of the SysEx commands for parameter changes - one example
F0 43 10 7F 1C 07 37 03 01 43 F7
The '03 01 4C' (table of p.213) means:
1. 37 -> address high
2. 03 -> address mid (0p) so part 4
3. 01 -> 'Assignable Knob1 Name 2' (2nd character of knob 1 name)
2. 43 -> an uppercase 'C' in ascii hex
That one command changes the 2nd letter of the name for knob 1 for part 4. Since the current name could be 16 characters long you would have to send 16 of those commands, one for each letter position, to be sure you have overwritten the existing name.
That is why people have been wanting tools to do things like that. There is an ESP DAW plugin for the new Montage M models.