Hi @NewcombR ,
Could you please share a bit more about the error when you ugrade?
Do you mean that canvas app in your managed solution set as a managed component?
Currently, if you import an managed solution into a target Environment, you could not edit the components within this managed solution.
Please refer to the following article for more details:
As an fixed solution, please consider remove/uninstall the managed solution from your Test Environment, and then import the updated managed solution into your Test Environment again.
If your solution is still under development, I think you should import your solution as a unmanaged solution rather than managed solution. Then you could continue to add and remove components to this Solution within your Test Environment.