My first impression is that it breaks expectations for common operations:
1. Two-finger sideways panning does not work, it zooms erratically; 2. Click and drag pans instead of drawing a selection box; 3. Shift + Click or Cmd + Click does not add item to selection; 4. Two-finger vertical swiping does not zoom when hovering an item; 5. The zoom disregards mouse coordinates, always anchors from the center of viewport;
Still not sure how to select multiple items. I'd recommend you get the fundamentals of navigation/edition right, otherwise it's unworkable. Even for a POC. I can't even explore the scope of built features with excitement because these issues make it super frustrating, makes me wanna give up immediatelly.
Misc:
6. I expected snap to grid; looking for the option but there's no app menu; 7. Adding icons successively stacks them on top of eachother, which is adds repositioning overhead; 8. Very easy to wrongfuly scale small items while attempting to move them; 9. I'm seeing at least 250ms of lag for openning sidebars and getting visual focus feedback;
This last one is tough feedback, please don't take it personally. I want to join the waitlist for notifications of more mature versions. But since you shipped publicly too early, it makes me question if it's worth and the team behind it can actually deliver up to my expectations. In other words, I feel like it jumped the gun. Bad first impresssion for a technical audience.
The bar for minimal UX polish nowadays is very high, all the fundamentals have to be solid, I would gladly trade a thousand features for these solid fundamentals. That's my expectation of a POC: low on features, high on polish.
If it's any conforting, consider that the only reason I bothered to test it and write this feedback (in a rest day with very acute right hand tendinitis) is because I think it's a very cool project idea.