Hi! I'm brand new and doing an extremely complex shoot and need to do multiple shots within the same setup with multiple characters and props.
I don't want to rebuild the scene every new shot, and it looked to me like the freeze scene option would be perfect for designing all the setups I need. But it isn't there...
Is there another function like freeze scene that I can use?
Please help.

The scene freeze feature was a dumb feature that we've retired. It has been read-only for several years and is now completely removed. Basically, there was no difference between a scene freeze and just saving under another new new, except that it gave us an uninspectable copy of the scene where objects couldn't be reference-counted, which created paradoxes that led to certain crashes.
Just save under a new name. You can also save a scene in the My Templates folder, which gives you the option of making a new scene based on the scene when you open it.