Tab to open: "filters", "layers" or "legend", depending on what the
profile enabled at initDesktopPanel().
true if the tab exists and is now open, false if the panel is not built, the
desktop breakpoint is not active, or no such tab was declared.
Opens a side-panel tab by id, without toggling.
Calling it twice with the same id leaves the panel open — that is exactly what separates it from a click on the tab, which closes an already-open tab. Use it to drive the panel from host code (a menu entry, a deep link, a workflow step).