I remember using it in a newer Unity version, but I can’t find it in
2020.3.29f1
Presumably because you’ve not added the package which it resides in i.e. Tilemap Extras.
Tilemap Extras isn’t a preview package, it’s at v4.0.2 released on September 04, 2023.
It looks like I’ll have to update the project to a new version then
