I don't think it's a Ventura issue as iMovie is notorious for consuming large amounts of memory as it loads your movie library. Your original screenshot has iMovie using 55GB of memory. Obviously you don't have 55GB of memory configured so a large majority of this is virtual memory. Smells like a memory leak in iMovie. About all you can do is quit iMovie and try reducing your movie library size or create a new library for each project.