No its not possible. There is a workaround which is kinda ironic.
You can use the old workspace as a container for multiple Playgrounds, each tab will contain a new playground.
So issues the command Workspace open in a plaground and then go to the righ menu (down arrow) , choose window group and drag your playground to the tabs bar. Of course you can add as many playgrounds as you want , each in its own tab. Works like a charm :)