[SiriusHardware]

Intel Hex files are just carefully arranged text files which can be edited in a plain text editor like Notepad. You can't (easily) edit the actual lines of hex that way because any change in the data on a line will also require a change in the checksum byte at the end of the line.

I've never tried it but if you try adding your instruction text on to the very end of the hex file the send14 script may just read and ignore / discard the extra lines. Just try it and see. Try to avoid using the Colon ':' character because the uploader script uses that as a 'start of Intel Hex Line' marker.