How do I disable Ctrl +F?
No, this is not possible, CNTL-F is a web browser function that can't be disabled just for the Canvas web site. The only way to achieve this would be to insist that the students use a special web browser such as Respondus' Lockdown Browser.
Can Ctrl F be tracked?
Nope, not possible. On some browsers you can catch the key combination Ctrl + F , but you can't spy on what the user searched for. On other browsers you can't catch Ctrl + F at all.
Why does Ctrl F not work in Chrome?
Ctrl+F makes a page search and with Docs, the document IS the page, thus Chrome considers it as the same thing and it overrides the browser page search.