I had this same question.
I'm trying to watch a video on half my screen and take notes on the other half.
Yes, I just found the answer not form this thread but by seeing no solution has been presented and looking harder.
I think I have the web version especially since I use a Chromebook and its hard to find apps for it but I'm not sure.
Forgive me if I am assuming incorrectly.
I navigate my browser to evernote.com
There is a button on the top right that has two arrows opposed diagonally - it makes the notebook list of notes disappear to the left so that only the current note is in the browser window.
Here is a 22 second video demonstrating this - https://youtu.be/g7F-gUMITsk
Acer Chromebook R11 Chrome OS Version 69.0.3497.95 (Official Build) (64-bit)