I needed to figure out a way to disable my touchpad on my chromebook when I had my mouse plugged in as I was accidentally constantly brushing my thumb across the touchpad when doing typing and only using my mouse for cursor movements. Though there is no default way in ChromeOS to disable the touchpad while mouse is plugged in, there is a hidden flag in Chrome that you can enable that allows you to use a keyboard shortcut to disable your trackpad and enable it again when you need to.
Here are the steps to disable trackpad on Chromebooks
The first thing you want to do is open your Chrome browser and type in “chrome://flags” in the address bar and hit enter.
Then search for this specific flag “Debugging keyboard shortcuts”
And enable it.
Then you will have to reboot your Chrome and when it comes back up the Search Shift P key will be the functions you use to disable/enable the trackpad and you can start testing it anytime.
If you are like me and your thumb constantly hits or brushes against your trackpad while typing on your chromebook this can be a very useful tip for helping remove the accidental brushes and clicks that distract you from working or interrupt what you were doing. I know nothing was more annoying to me than typing in a document or editor only to have my thumb accidentally open up a new tab or click on something unintentionally.
Let me know if this tip was helpful.