Found this post and your other one while trying to solve a similar issue …
Mosaic is available with RTX Desktop Manager, however it’s unavailable for non-Quatro which was a wash for me.
NVIDIA RTX Desktop Manager Download Page
What ultimately worked was setting up a custom canvas layout using FancyZones via Microsoft PowerToys.
Microsoft PowerToys Main Page
With the custom layout I’m able to maximize windows across any number of monitors or snap windows into predefined areas as needed. It’s a productivity dream.