I have my MacBook M1 as my personal laptop, and I have a Chromebook as my work laptop. I don't really like the trackpad and keyboard of the Chromebook so I wish to use my MacBook just for the display, keyboard, and trackpad (just like external display/accessories). Is it possible to achieve that?
Since a lot of software isn't compatible with Chrome OS I had to search around a bit. However, I found Google Chrome Remote Desktop which apparently is a native remote desktop solution for practically any device which has Chrome installed.
This would mean that you can essentially use your MacBook (including its display, keyboard and trackpad) while being remotely connected to the Chromebook. I can't test this solution right now but it seems to have worked for other people who had a similar problem.
Using this solution it won't be possible to use the MacBook as a second display (as stated in your title), just to mirror the display. Nevertheless it should allow you to use your MacBook as if it was the Chromebook (which you seem to want to do by your description of the problem).