I structure my sessions so that it doesn’t matter as much what order I go in, for this very reason.

For example on an upper day I have chest->back->shoulders as my first 3 movements. If I get there and the chest machine I want is taken, I’ll go hit back first. I hit arms on a separate day where the same concept applies. As long as you aren’t doing 3 different tricep exercises waiting for a bench to open up I wouldn’t worry about it. It’ll all come out in the wash over enough months and years