'show more/less like this' should work[0] with cowboy's for you feed. 'more/less' was proprietary for discover but they've rolled it out to other feeds now[1].

I think it's part of an interactions object passed to the feed operator. You can see what's potentially passed here[2].

[0]:https://bsky.app/profile/spacecowboy17.bsky.social/post/3lxx...

[1]:https://github.com/bluesky-social/social-app/pull/8672

[2]:https://endpoints.bsky.app/#bluesky-app/tag/appbskyfeed/POST...