When you execute the save in the Studio One side, you have to send the information that you edit something to Studio One side.

The Piapro Studio plug-in is the special specified VST/AU plug-in, and It’s not possible to send Studio One the information that you edit by only editing on the Piapro Studio plug-in.
When you close the window after finishing the operation in the Piapro Studio plug-in, make sure you send the information of your edits and execute the save.

In the Studio One, you can send the information of your edits by only closing/opening the plug-in window.

If you worry whether you saved correctly or not, save by the item “save by another name” at the “file” menu.