Currently, OpenMPT's pattern editor follows the standard 2nd generation tracker paradigm of having 3 ascii only characters, the last of which is either the octave number, or the octave number is not displayed. There is nothing wrong with it when using 12-EDO, however, when using custom tunings, the notation can become really inconvenient to the point where the only way to do it is to simply number the notes and have a reference nearby.

Enabling the possibility to adjust the note column width would make more informative notation possible (adding non-ascii character support would be even better but it's less important). Without knowing too much about OpenMPT's codebase, I think that the best way to do it would be to make it a mptm-exclusive feature and store the column width in the song file itself. This would keep the interface unaltered for legacy formats.

However, if this feature is viable at all, any working solution would be nice.