The cable I got with mine has no markings. I got a variant called "Mecha edition" for some reason, so maybe that's why.

The shells do have markings, but it's not hard to tell left from right by the shape anyway.

I used a song where I knew which side the bass was coming from as a reference to figure it out.

Btw I ordered an extra cable with a mike together with the IEMs, and it doesn't have any L/R marks either. Bought from the Linsoul website.