Still very temporary, and new rooms will be unlocked via the research screen, but I've nearly got this functional enough to allow players to grow their museums to house any number of specimens (probably won't put an upper limit in).
Looking forward to being able to have an exhibit that's just headless sauropods.
Can now add, remove, and traverse between rooms. Map works for fast travel, but you can just use a door to go to the next room as a more "immersive" option.
Still rudimentary (and made less exciting by only having one room shape in the game), but it's usable.
Here's a little concept I scribbled last night while waiting for a rough cut of the most recent progress update video to render.
I'm a little embarrassed to share it because it's not even remotely accurate, but a) it's important to overcome that (with a disclaimer, of course), and b) concept pieces are about communicating ideas/intent rather than being perfect ^_^