As the title says, add section property and material to the Members spreadsheet in the physical modeler. This might not be "consistent" with how things are done in the spreadsheet ribbon, but so often when modelling the user wants to group the members by "description" (which you have allowed and is great) and then wants to change the section for all those members. Or I may add a member later and just want to copy/paste the section and material from the other members with the same description.
Thank you for posting this idea. However, I think you might find the capability already exists. If you want to select all the members that have a specific description, then find any one in the Members table and right click, then click on 'Find and Select' this will select all with your given description. Then switch to the Properties spreadsheet and they are all selected. Double click on any one of these properties you wish to change and pick the new property from those defined in the catalog. Then right click and pick 'Assign Selected', all your selected members will be assigned your new property.