I wonder if this is possible without an automation/script?
A dashboard button with a toggle action BUT: the action may not execute if another switch (entity) is on.
The conditional card could be a way around it, can it also be done as in my imagination?
I think the conditional card is the way to go - two identical button cards, one conditional on the switch being on, the other on it being off. Then in the “on” card, the tap action is disabled.
Edit: I’ve got one a bit like that which changes the name on the card (from “windows” to “window”: