Timeline as a clip in a Multicam

Hi there, I'm confused if it's possible to do that trick (or something like this):

I have 3 files from 3 cameras like a standart podcast situation.
BUT! I need to do an extra splitscreen view from two cameras (two files) and I'm doing it in a new Timeline.
SO, right now I have 4 items for my multicam view to edit that whole story - 3 files and 1 timeline with a splitscreen, but it's impossible to put that Timeline in a new Multicam.

Any thoughts how can I do it without rendering a whole splitscreen Timeline to a new file and how it's possible to get a Multicam with 3 actual files plus splitscreen view from two of those files?
Thanks!

You can't edit the Multicam, Flatten it, and then do VFX (Split Screen) on the appropriate clips?

For the split screen create a compound clip just of these scenes. You can even add it to the multicam as a separate angle. So if you open your multicam on the timeline you would see:

angle 1
angle 2
angle 3
angle 4 (split screen composite)

Building the split would be tricky, scaling, positioning, and compositing.

I think you can probably open the multicam clip in its own timeline, do split screen effect there and later when you flatten it, keep the grade. If you do it form color page with output sizing, if I recall, it retains the crop and all that. You can also try working on the cut page with sync bin when working with multicam footage.

If you do crop or scale within the Multicam timeline it will use the resolution of the Multicam timeline not the resolution of the source file . For instance if Multicam timeline is1920x1080 but source file is 3840x2160. The crop or zoom will use the already file scaled to 1920x1080. If you flatten first you will go back to source resolution.