GlyphsReporter to add custom parameter

Is it possible for a glyphsReporter plugin to add a “note” custom parameter if it doesn’t exist, but only when it’s run for the first time on the current font? I’ve been trying this but end up crashing the app all the time.

I figure out the code to add the note parameter, but don’t know where in the script to put it.

Please leave the question whether it is advisable to do so.

I don’t think the reporter is the right tool (but as I don’t know what you try to do I might be wrong). Can you explain a bit (maybe per mail)?

Case closed.