Emulate an 8K display with TD on macOS?

Im trying to get Apple Keynote to span across multiple monitors on a mac. Wondering if there is a way to emulate multiple external displays to read as a single monitor.

Im hoping to have 2 x 4K monitors show up as a single 7680x2160 display to Keynote in presentation mode, or perhaps more 4K monitors for an even bigger canvas. Curious if there’s any clean/reliable way to do this in TD, and perhaps even output the emulated span displays out via NDI or similar, to another server.

Matrox and Datapath boxes only support a max of 4K from my knowledge/experience.

Of course Windows machines can do this spanning much more easily, but this particular client wants us to accommodate via Keynote/macOS.

You can span monitors on macOS like 7680x2160, but they need to be present and connected to the system so the OS creates the canvas. You could look into EDID emulators which trick the OS unto thinking a display is connected, there are small ones that look like a HDMI dongles that could do the trick (search 4K edid emulator).

Also, I think for spanning you might need to turn off ‘Displays have Separate Spaces’ in System Preferences > Mission Control settings.