Currently you can open several VST editor windows side by side by enabling Keep Editor Open for VST X and open VST Y through the console. That's great!
However I would like to suggest a second option to open VST editor windows side by side, by opening a VST editor from the console while holding a modifier key (CTRL, ALT etc.).
So when I have VST X open and click VST Y in the console or on the tab in the VST editor window, while holding e.g. CTRL, VST Y will be opened in a new window, not affecting any other open windows (regardless the Keep Editor Open state of other windows).