Building outfitting system with common accessory-mounting feature

A prefabricated system for outfitting a building space includes an architectural product (such as a full-height permanent building wall, a post-and-beam product with overhead frame, and a drywall-covered wall), a furniture product (such as a partial-height wall, a partition, and a desking system), and a plurality of accessories. The architectural product includes a structural member with horizontal and vertical accessory-mounting T-slots, and the furniture product includes structural trim pieces with identical vertical and horizontal accessory-mounting T-slots. The plurality of accessories are constructed to stably engage any of the accessory-mounting slots at a selected location along the slots. Some accessories can be attached to and extend between the two products, such as an accessory screen that extends between a post of a post-and-beam system and an end of a partition system.