Possible to create a multiplayer game with squiffy?

In theory - yes. But you'd have to be pretty comfortable with Javascript and server side scripting. You'd also need to self-host on your own server. To be honest, you'd have to modify Squiffy's underlying engine so extensively you'd be best off writing your own custom framework.

Certainly no "out the box" solution available.

I did for example play around with saving user progress to a MySQL database rather than the localcontent solution used by Squiffy. Just doing that required a lot of reverse engineering. So getting a true multiplayer system set-up would be a lot of work.

This was brought up in Quest...
There may be some ideas there...
But, are you talking about a network type game???
Or several people around the same PC???

saving user progress to a MySQL database rather than the localcontent solution used by Squiffy

That sounds fun to play around with!

Yeah, but it is going to be

HARD

And not multiple people on one PC

Yeah, it's a bit of a pain in the ass because of the way in which Squiffy is set up to write to local storage, with separate calls for passage progression, attribute modifications and other modifications to the DOM. Wanted to consolidate all under one user triggered function which would then be saved to database. Not too hard but as mentioned just some time consuming reverse engineering of the default Javascript files. Never actually used it in the end :)