Hello, your project is safe as long as you don't overwrite it by saving, don't worry!
By the way you may want to save a couple of batch files to launch the correct version of Spine depending on the project, I use them a lot!
On windows the procedure is easy. You open a text editor and type in:
cd C:\Program Files (x86)\Spine
Spine -u 3.6.53
The save and rename to Spine3.6.bat so next time you just double-click it to start Spine 3.6 immediately.
