To start with you are aware your system can support upto 64 GB of RAM! As you can see here Apple T/N iMac memory specifications
Why do you think you need this much RAM? Not many apps are even able to access this much! I know of only two presently and they are both in Beta! Video editing and rendering is about the few uses most people will need this much.
This is a complex issue! As you have the physical limits of the RAM SO-DIMMs as well as the ability of the system to address all of the lines. This gets into the wiring of the socket as well as the logics ability to recognize all of the signals at the physical level and then the OS and the apps you are using would need to able able to leverage all of the RAM space.
Using multiple apps concurrently is presently the only way you could do this if the OS is able to recognize the RAM.
Frankly, I would leave your RAM alone here and make the effort to upgrade your PCIe/NVMe SSD to a larger one! I’ve been putting in 2 TB drives in for music and video artists and others working in the arts. I only go with the custom Apple Samsung SSPOLARIS drives. Setting it up with the OS and Apps and leaving the rest of the drive free!
Given how new your system is I would go with this other option, setting up an external RAID’d SSD drive like OWC Express 4M2. Or these newer units: OWC Envoy Pro EX or OWC ThunderBlade that way you don’t risk your warranty as well as the risk of damaging something in the process as opening the newer ‘Thin Series’ is not easy and you could damage the display if you don’t use the correct tools and technique!