Is there a way to tag others on steam?

I am aware that you can add tags to people on your friendlist, but is there a way to do it to people that aren't? I've come across a few people in games that I would rather not play with on my team and the games don't support a blocking feature, and I'd like to add a tag at the end of their name to identify them.

Currently have written the names down in a spreadsheet but that is going to be a clunky way of doing this going forward. But can't think of anything better lol.