On second thought. I would scrap the old panel altogether and for a very good reason @George
Check this image. A SC open in a tab and a SC open in the old panel.
What are you saving when you click on the save button? It’s rhetorical. I know what I’m saving but it’s going to create a UX havok and impact specially new users.
Am I saving the tab? Am I saving the old panel? What if I made a stupid small change to the old panel SC I forgot about but I click it thinking I’m saving the tab. Bad things can end up in production. What about the modals that pop when you have unsaved work? How would I know which is it affecting.
From the bottom of my heart. Be done with the old panel altogether.