Hidden panels register a screen edge so they can appear again when you “touch” the edge of the screen with your cursor, and there is no option to disable it unless you have a fullscreen window.
The only workaround I found for this was to completely hide the actual window holding the panel, and it requires a third party plugin to do that. It will hide the panel completely so you need to manually make it appear again, see Show/hide main panel with a hotkey - #14 by luisbocanegra