Hello!
I have the same need when I freelance, and what I do is create batch files to launch the correct version for me.
On windows, in a text editor of your choice, paste this code:
cd C:\Program Files\Spine
Spine -u 3.6.53
Change the folder to where Spine is located if it doesn't match mine, and change the second line to the Spine version you need for the project.
Then save the txt and rename it by also changing the extention into a batch file to something like this: "Spine 3.6.53-nameofproject.bat"
This way you'll always know what project it is for and the Spine version you're using!
