Clear Physics mode has been one of the most extremely useful features of NeoLemmix. As such, I don't see why such a function would have an option to either have "hold key" or "toggle".
The "hold key" function should be removed. Especially in levels that require a lot of planning or have lots of objects such as traps, teleporters and locked exit/unlock buttons, the "toggle" option is 100x more useful in case you want to spend a good amount of time checking over the level and hovering over each object and knowing which is which.
I would even say that "toggle" should have been the default option for Clear Physics mode in the first place if one were to open NeoLemmix for the first time.
Yeah, I've been thinking about removing that option. Unless anyone objects, I'll remove it.