I was attempting to use ReplaceBlock but I got this message:

Missing Dialog: the 17CRhInstanceDialog dialog for this command is not yet implemented

I’m pretty sure this is currently not developed, but incase it’s a bug I wanted to bring it to your attention.

ReplaceBlock is available here using the latest version of the WIP 5A808w. Check that you’re running the latest build.

I see this here. It’s a bit tricky to reproduce, but I was able to. Definitely a bug (MR-1968). Thanks for reporting it!

I should note that only the dialog for selecting from a list of other blocks is not working…you can still pick an instance of another block and replace the existing block instance. It’s a sloppy workaround, I know…and a temporary one for that matter.