On Looker Original instance v26.12.9 and have noticed a few weird things.
I like to use constants when defining Connection names in Model files. In the Manage Projects page, I see errors about my constant isn’t a valid connection name all of a sudden (Connection '@{bq_conn}' does not exist). I’m still able to run the Explores for those Models still just fine, though.
Also when I create a new model file, I can’t seem to add it to a Model Set. Doesn’t matter if I use a constant or not for Connection name. And again, I can still use any Explores I include in the new model file.