Hey @just_jake - I responded to your PM, but wanted to at least share the high-level feedback here.
The short version is that I would recommend against trying to target tile-holders as they are an internal implementation detail (functionally transparent wrappers) and will likely get removed from the DOM in future updates.
Reading between the lines, if the intention is to change the position of a tile, I would generally recommend against it as the positioning is managed via JavaScript and any CSS trying to change the position would be fighting against that. Of course, sometimes people just want to scratch an itch and I can totally understand that… just know that it’s unsupported and not recommended.
If you feel the underlying use-case you are trying to solve via CSS might have broader interest from the community, feel free to post it as a feature request! (Just to be clear, I would suggest framing it around the use-case not the attempted technical implementation though. eg. “I want to be able to freely position tiles on a dashboard rather than in grid spots”)