I think the problem here is that Intel HEX files have CheckSum's on every line.

If you edit a single character anywhere in the file, the file will no longer be valid. So not only does the editor have to format things so you can read them, but it also has to recalculate checksums after each change.

Not likely to find a Freeware for that.

It would probably just be easier to create the file using MPLAB.

A series of db statements should make it pretty easy to edit. But if you're just editing existing files, then that won't work too well either.
<br>