In the file gc_rules.py, I've added the '-' for the following rule.
['^ *[*+-] ', False, '#774p', 'p_md_liste', 4, [[None, '~', '*', 0]]],
It works fine.

But I wanted to add a suppress rule for double spaces at the end of a line, since it's a markup for a "simple" carriage return.The following line should do the job, but somehow, I'm still getting "Espace·s en fin de ligne à supprimer."
['[ False, '#776p', 'p_md_nouvelle_ligne', 4, [[None, '~', '*', 0]]],

Did I write the rule in a wrong way ?
Thx for your help.
Fred