Also, this is a truly beginner question, but when using the iOS simulator, how do I simulate gestures like pinch and zoom? I tried using my laptop trackpad, but nothing happened. I can just use the mouse to tap and drag. UPDATE - nvm - I Googled it. You do OPTION+Left Click. Now that I know how things tend to work on the simulator, I can google more stuff.

Just one update - when I tried a program written for Mac using Catalyst, I ran into your issue 7, but the only simulator I could run it in was an iPad. Is there any way to run Catalyst Mac examples on a Mac, or is the iPad simulator the best I can hope for? Thanks for clarifying, Jeff

If it would be useful to have a concrete example, here's a simple sample code example I'm interested in that won't run: https://developer.apple.com/documentation/metal/onscreen_presentation/reading_pixel_data_from_a_drawable_texture/

Or, as a more serious use, the production of custom libraries to aid you in making great future apps.

Just as a side comment - nowadays, XCode projects seem to be tightly bound to an actual App (typically an iPhone App) that you intend to have in the App store. Which is fine if that's what you're after, but what if you just want a project that's not for a specific App? Just to use as a learn how to program the Mac sandbox? How would you set that up?