There are 780 available global variables. I’m surprised you are running out but if you are, you are. Maybe you should, however look at a strategy to reduce the number of global variables. For instance, I use bitmapping for simple on/off state. With this I can map up to 32 toggle button functions with a single global variable. A variable is 32 bits.
I have not had any stability problems and I run multiple instance all of the time. I use a APC-MINI to control voicemeeter while my Win 10 PC is powered up. Then I do support on a separate instance. Sometimes I have to run 2 instances for support using one as an emualator and the other as a test target. I have heard recommendations against multiple instances but maybe these are based on older version of MT Pro as I have not ever tripped over any stability issues.
Not if they are using different virtual ports. On Windows, a given port (virtual or otherwise) can only be opened by a single application or device at a given time. You have up to 18 virtual ports on MT Pro (9 in and 9 out). If you need more, you would need to purchases Unlimited Named MIDI Ports.
Beyond using different virtual port, I would say watch out for keystroke and mouse sequences and make sure they are different on each instance as they are not differentiated between instances.
Here is a reference to bitwise operations if you are interested in exploring better use of global variables. As I say, I am currently using 2 global variables to control 64 LED’s on my APC-MINI to track Voicemeeter channel status.
Steve Caldwell
Bome Customer Care
Also available for paid consulting services: bome@sniz.biz