I could not find any way using FMP to do auto fill of the comments field.
I try to name a field with self evident use and also makes easy Labels on layout too.
CustomerLastName or StreetAddress [self commented and self labeled]
Also, if you acquire a copy of FileMaker Advanced, you can generate a Database Design Report that will, among other things, list every field in every table in your file and layout and script that uses it.
Thanks for the answer: @PhilModJunk
I should have specified that I'm already using the advanced version. So I can create and use DDRs. Just I'd like to extract certain information from it (should be no problem from the XML) and automatically write it to the field comments. So whenever I'm working with my field, I instantly see where they are and which script uses them. Currently I do this by hand, to stay oriented. Helps me a lot when touching a database a few months later.
thanks for your comment. I'm already doing so.