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.