From Synfig Studio :: Documentation
Panel tabs are the small square tabs (filled with an representative icon) along the top of each of Synfig Studio's dialog windows. You can rearrange the layout of Synfig Studio by dragging the panel tabs around.
You can move the Panel by dragging the Panel tab :
- within a single dialog to rearrange their order,
- to place it using the Placement Widget,
- from one dialog to another to group them how you like,
- or even drag them to the desktop to make a new, separate dialog.