Featrue request: option to occupy space in panel even when buttons are not visible

[anupam207]

Use case: I have window buttons placed at rightmost part of the panel and visibility set at CURRENT_WINDOW_MAXIMIZED to avoid confusion. So when I switch between maximised and unmaximised windows, as window buttons appear and disappear, other icons at the right part of the panel keep switching places. If window buttons occupy the space even when they're not visible, the positions of other icons will be consistent.