This is really an infinite canvas window manager, but only for terminal windows.
I looked for a general infinite canvas window manager and discovered InfiniteGlass[1]. I wasn't able to install it though, even on Ubuntu Mate 18.04, which the installation instructions are supposed to be tested for.
I've switched to KDE recently, using its default terminal, and I feel like I can't miss things like opening the file browser from the terminal or vice versa anymore, so now what I really want is an infinite canvas desktop environment.