Sort Revit sheets by number/prefix.

[rossMU4L8]

I started a new project and have 50 sheets or so and would like to sort them by number/prefix.  For example, I would like all A2.XX sheets to be listed in the project browser under an expandible heading 'A2', all A3.XX sheets to be listed under an expandable heading 'A3', ... and so on.  I have done this on previous projects and remember it being very easy, but I cannot figure it out on this new project.  I am working in 2018.3.  I have attached an example of what I am trying to accomplish.

Any help is appreciated.

[ToanDN]

Create a parameter assigned to Sheets category, select A2 sheets and enter A2 for that parameter field.  Edit Sheet browser organization and add that parameter and Sort by it.