Hey, glad the improvements have had some effect. Gradually trying to upgrade things. Thanks for letting me know about that bug, I've just pushed a hotfix to address that.
In Sandbox Mode the idea is currently that you can press on the portrait of the NPCs to take control of them and use the character editor to get your desired character. I'll grant that's not the most elegant solution with an extra step but at least a workaround for now. Ultimately I'm still planning to add finer UI controls and quality of life upgrades.