RH 2017: Can I define a variable for use in the Output Folder path for both parent and child SSLs?

In our Responsive HTML5 output, I have a "version" number that I'd like to define as a variable and use it in an output folder's path here:

This is my parent project in a large merged help project.

My child projects already use a version number that I have to udpate for each child project:

Currently, we have about sixteen child projects and each new development cycle (every few months) I have to always update this variable value in each one. Because it's a manual process, we sometimes forget one or two.

Is there a way to define this in one place for all my parent/child projects and have all the SSLs use that single variable value?