Maybe I'm not understanding what you want exactly, but it sounds like what i3 and Sway already do. Workspaces are created as needed and are specific to that monitor, so if workspace 3 is on the right monitor, you can jump to it with super-3 even if you're on the left monitor. You'd be looking at workspace 3 on the right monitor plus another workspace like 1 or 2 on the left. Each monitor displays a separate workspace which can be changed without affecting the other.
You can also define rules in the config so that certain programs will open in certain workspaces every time, and you can move the whole workspace to the other monitor (not a default keybind iirc) if desired. Good in a portrait+landscape monitor setup for if you need your browser to be wider for a little bit.
You can also define rules in the config so that certain programs will open in certain workspaces every time, and you can move the whole workspace to the other monitor (not a default keybind iirc) if desired. Good in a portrait+landscape monitor setup for if you need your browser to be wider for a little bit.