Salamander! They have wide range of racks and many can be configured to suite your needs. I had a Twin 40 and a few years later I added a couple new pieces of gear. The parts were ordered and the twin 40 became a triple 40.
https://www.salamanderdesigns.com/synergy-system/
https://systems.audiogon.com/systems/3373#&gid=1&pid=2
https://www.salamanderdesigns.com/synergy-system/
https://systems.audiogon.com/systems/3373#&gid=1&pid=2