I installed Vimium for my Chrome browser to use but I noticed that Chrome shortcut keys take higher priority.
For instance, if I try <C-u>, instead of scrolling a page up, I see the source code of the page.
How can I configure Chrome or Vimium to use Vimium shortcuts rather than built-in Chrome shortcuts?
You currently cannot map any default Chrome shortcut keys defined already. That is unfortunately one limitation of Google Chrome Extensions API. The Extension team is familiar with such restrictions, and they have it on their queue for future APIs.
In the meantime, try to pick a shortcut that doesn't conflict.
Hope that kinda helped.