I have mentioned the absence of multiple instances in Rapid PHP as a deficiency, including in my review. I have also mentioned that I understand how difficult it might be to modify Rapid to achieve multiple instances.
That got me wondering what it was I really needed and what might suffice instead.
If I am working on a project today and I exit Rapid, when I start Rapid again the files that were in the editor are restored. That's handy.
By contrast, if I switch projects without leaving Rapid, my editing state from the first project is not restored when I return to it.
What if Rapid could remember a "workspace" for every project? Then I could switch between projects A, B, and C with impunity, resuming each project exactly where I left off.
I don't think this is as convenient as multiple instances but because Rapid seems to open projects, well, rapidly, it would be a very good alternative to multiple instances.