Windows – Multiple monitors – add border collision? (Windows)

Pretty sure there's no way to make it seamless from the smaller to the larger screen.

If you right click on desktop, choose Personalize, Display Settings, you can drag the smaller screen higher or lower in relation to the bigger screen to determine exactly where you can cross over from one to the other.

I'm not sure if UltraMon has any settings like that.

Edit: I just installed UltraMon beta version. The beta version had a Display Settings panel that does that same thing. You can change the relative position of the monitors to one another in order to control what areas will be blocked/open for crossover.

You could use Windows built in tools. On the resolution settings screen, drag the "middle" monitor down slightly in the layout section at the top, so that hitting the top right corner of the middle monitor will cause it to hit an invisible boundary.

Then you'll just need to ensure you hit the top of the screen before going to the right of the screen.

I've done it for mine, and it's worked for me :)