It would be great if we could mark attributes and associations as deprecated, like we can with operations in REST services. Now you have to rename them or use the documentation field (with the last it could be easily overlooked). This way your domain model stays clean and you don't have to rename with possible lots of changes as result.
When an attribute or association is marked as deprecated, maybe it can show up with strike-through styling in your domain model, connector and other selection pop-ups so you can't make a mistake of using an old attribute.
Then after a while and after your necessary conversions or migrations have run you could possibly search on deprecated items for clean up purposes and delete them once and for all.
In addition to your visual indicators (strike through) it could be worth while to have a warning displayed in the error/warnings pane.
In the later versions of studio pro this could also be displayed in microflows and pages with the counter icon above the usage of the attribute or reference.
I’m looking for this feature too. I have an attribute that now appears to be on the wrong entity. I don’t want to remove it as I don’t want the app to break immediately. I would much rather create the attribute in the correct place, mark the old one as deprecated and slowly make the changes as I understand the impact.