This isnât an area (you can tell by following the shape of the area boundaries), so manipulating area shapes wouldnât have worked here.
The icon in blue is a universal symbol for âmenuâ, so try LMB/RMB on that and see whatâs in there. Iâd also look at the dropdown in yellow.
If you donât see an obvious solution, I would also try replacing the Viewport with a new one. Use the icon in green to change this area to a different one, then back to a 3D Viewport. I have no idea what the panel is/does and I canât seem to create it, so unless someone else has more insight, youâll have to try these things for yourself and see what happens.
As an absolute last resort, just delete the whole workspace and create a new Animation workspace in the top menu, but it really shouldnât have to come to that.