This demonstrates the functionality that you speak of.
It's not the full screen version that you're looking for.
You have to be rooted and it's not particularly easy to install.
Then you need a full screen app that's blank and handles the pen data.
https://xdaforums.com/posts/88706195/
The left Android is the slave (which would be the PC).
The right Android is sending keys and XY out. The inset frame is touch sensitive.
I forget if there were some issues with getting Windows to accept the input if you kept ADB or MTP enabled too.