Panels (including the root widget) and tabs can contain either tabs or regular widgets, but not both at the same time. When a panel is empty you should be able to select “Add tab” in the right-click context menu. If you’ve already created widgets in that panel, you can select them all, hit ctrl+x (cut), add a tab, and paste them all in the tab. Using the project tree (left panel) can help right-clicking on the appropriate panel.
Might be helpful to add a simple description of how to do this to the docs. I searched in earnest and couldn’t find an explanation. Didn’t notice the “add tab” option via right click until you explained here.
But then what? What’s the next step? I want to create a tabbed lay-out, like the Chrome browser.
So i’d like each tab should take me to a different full-screen with it’s own set of widgets.