The message pane or the description window? The message window gets triggered by the envelope whereas the description window gets triggered by the form icon.
Reason I ask is because I know how you can undock and dock the description window / pane (it also looks like a pane) but I fail to see how you’d undock the message section, that’s why I wonder if you didn’t mean the small window.
The description window has 2 icons in the top right corner. The cross is used to close it, and the icon next to that is used to dock and undock it.
However… I’m talking about VP 14.2 with the sleek interface, if you’re using the regular interface (default with an older version) then you should be able to dock the floating window by dragging and dropping. Just drag it by the title bar and move it towards the bottom of the screen, you should eventually see an indicator which highlights where the window would be placed.
I hope this can help, if not then maybe you could share a screenshot or mention which version of Visual Paradigm you’re using?