Some of the gene markers associated with tenderness have been identified.
First-generation that I'm aware of was the GeneStar tests... A number of Angus, and a few Shorthorn sires had test results available - and I used them as selection criteria behind epds and pedigree... particularly using sires with as many of the (at that time, 6 - 3 pair) gene markers. Used several 5 & 6-star Angus sires, and several of the Shorthorn sires we used had 3 or 4 of the 6 markers.
The newer genomic tests do include tenderness as one of the traits that they supposedly measure/represent... I've not looked lately at the Angus sires, as we've switched back mainly to Simmental sires.
The Simmental 'Shear' epd is supposed to represent tenderness, based on Warner-Bratzler shear force... and, again, I consider it, if all other traits I'm looking for in a particular sire are present; the more negative the Shr epd, the more desirable.
Granted, to date, no one is paying me any extra for breeding in tenderness... but I'm still selecting for it when I can... at some point, it might be worth something... if nothing else, I'm hoping someone is having an enjoyable eating experience, if they're eating steaks from one of my calves.