If I double-click a .sm file in Windows 7, it opens a new instance of SMath Studio. I would prefer that it open in the existing single instance of SMath and I switch between documents using the Pages menu rather than Windows taskbar. (Though it would be nice to have a split-screen view of multiple documents within SMath.)

Just wanted to note that this is a matter of taste. I do prefer the status quo. So, when addressing this, please provide a means to choose which mode to use.

Just one more note: If you find using the pages menu inconvenient, Ctrl-Tab might be your friend. It works just like in other multi-document applications.

Wrote

Just one more note: If you find using the pages menu inconvenient, Ctrl-Tab might be your friend. It works just like in other multi-document applications.

There's nothing wrong with the Pages menu, but it should be possible to view 2 pages side-by-side without having to manually resize them. As two instances, Windows 7 will allow this by dragging them to the sides of the screen, but this is the only benefit to having multiple instances, and it wastes screen space with multiple toolbars, etc. It would be better if it only opened one instance and had an automatic split-screen view inside.

For the maximalistic SMath users there is one more issue to note: separate instances of SMath run separate maxima sessions. The documents in a single instance share the same maxima session. This includes maxima settings like takeover of SMath functions (diff, lim, int, det, sum), assumptions and the like. You have to explicitly set the state if you want to switch between docs and you should always manually recalculate after switching. Also, there might be path issues with multiple documents.

Well, that's not "the only" benefit. SMath isn't perfect, and crashes sometimes. Having different processes for different sheets makes the crash less destructive, and intensive working with multiple non-trivial calculations makes this very noticeable advantage.

Another problem is that opening worksheets from a file manager or pinned bookmarks on the task bar will open them in new instances even if they're already open in the background of an existing instance, leading to multiple modified versions of the same sheet open in different windows, and if you save both, one of the sets of changes will be lost.

Is there any way to modify Windows "Open" action so that it opens in the existing instance?