setBookmark alternative in CM6?

I’m trying to add labels to the end of a line that move with the line when editing text (almost like they’re extra fixed characters at the end of a line that are always there). I think .setBookmark did that sort of thing in CM5. Is there an alternative to do that in CM6?

I’m now using a MatchDecorator but then I also need to decorate the match, while I actually want to decorate nothing in the document, but ‘just’ add an extra widget at the end of the line

I though I had exhaused searching the forum, but I did found a post which fixed my problem: Avoid replacing match in MatchDecorator (decorator to add link icon after URLs) - #3 by treyhunner