Invisible sprites can be usefull, if you walk into an invisible wall, it still hurts,
You should move the sprite to some unused coordinates, like -5000,-5000 if it should not be "active", and move it back when you need it again. You can also use the setspriteactive command, but I'm not sure how it will work with collisions and physics, I had problem using the virtual button active/inactive command, so I use the -5000,-5000 trick.
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AGK user - novice
Did Amiga / AMOS programming in the 90's, just started programming again with AGK.