Thanks to @stefano.menci, TIL that you can quickly and easily open a Form or Module in a new browser tab (not an IDE tab), in a new full IDE instance (not just an Editor!):
With multiple IDE instances, one might work in a second Branch, without losing your place in the first. Or move the browser tab to a new browser window (e.g., on a second monitor) for reference, or for copy-and-paste between modules. One might even be able to copy between different Forms (but I haven’t tried that yet).