When something REALLY needs to be marked, I'm still using the waxed paper that we got several years ago when a TSF member went to the US remember? We all shared a large quantity I think. It's very good, but is only used occasionally.
For short term marking, I have a chalk pen, or use tailors chalk [I even had one in a cracker this year, result!]
I've also been known to just reach for whatever pen or pencil is nearest, in a pinch. Bad Fairy.
A sliver of soap is brilliant for darker fabrics.
I've even used tailor tacks when I'm feeling like being conventional...
I had some of those marker pens that fade, but they fade to damn fast!