I fired up the map editor only the once but didn't even get as far as making experimental changes.

I took heed of the warning about the dire consequences of overwriting default maps with untested altered ones, capable of crashing the game but could not understand why they didn't follow this through and provide a "Save As..." button, so that you could start from an existing map, customise it and save it under another name.

I've only recently realised that you can, of course, do copy/rename from the Desktop but this slightly misses the point, in that you need to 'browse' the maps, see what they look like and see which ones inspire you to make edits on, so the need for a 'save as..' function, inside the editor itself still remains.

Someone please tell me I've overlooked something very obvious, or there's a hotkey for this, after all.