The ProSteel Hole Diameter list are accessible in different ProSteel Dialog box. If you ever wonder which file controls this, then this WIKI will explain and show you how it works. I would also discuss 1. The relationship between Diameter and the Workloose 2. Allow override of Values in Hole Diameter List.
You can allow to override hole values by setting it in the ProSteel Options. See screen shot and link below fro your reference.
The Hole Diameter List is accessible and can be edited. The video below shows how to access the file. Once you made the changes edit and save the file restart Prostructures and it should be available the next time you need to access the Hole Diameter list from any ProSteel Commands.