How to create a Tab Container

[hrykr]

I creating an editor where I can open for each file one tab (like in VSCode or UE). I saved root node and on file open I adding a tab to this node, using this function

self.tree.main_surface_mut()[self.main_viewport].append_tab

But when the main viewport is splitted, i got error when trying to add a new tab.
How I can create like a container with some background on no tabs opened, where i can open tabs. And it will placed like a tab without any controls, so i will be able to resize other tabs, and make it smaller/bigger.