Checking the 'Save' column in the Unity Pro Variable Editor ensures that the variable contents are included in the upload from PLC to project
when the 'update initial values with current values' is performed.

The Save attribute can be applied to all the variables at once by highlighting all variables (Ctrl-A), right click and choose <Data Properties>.
A Data Properties box is dislayed on the left.  Check the 'save' box and all the variables should take on the 'save' attribute.