Search engine shortcut URL - how modify it?

Description of the issue:
Under Settings > Search engines, in the “shortcut” list, I want to modify the URL for a shortcut, i.e this:

…but, as seen here, the URL is grayed out and doesn’t seem possible to modify. It is possible to modify the fields above the URL, i.e the “Search engine” and “Shortcut” fields.

Specifically, I want it to be a shortcut to search Youtube. How can I achieve this?

Thank you!

Brave Version (check About Brave):

1.60.125

Operating System:

Win 11 home

I discovered how to solve my direct need for searching Youtube (but not how to actually modify the URL for existing search engines, as detailed above)

The problem turned out to be poor UI - my actual need for searching Youtube is to be dealt with in the Site search section, just below the Search engines section. Fair enough. But the listed items there are somewhat misleading as they only deal with browser internal features and, more critically, the “Add button” is weirdly positioned. It would be better positioned at the indicated areas here: