The quick_bookmark signal is a keybinding signal which gets emitted when the user asks for it.
This is used to make the file chooser switch to the bookmark specified in the bookmark_index parameter. For example, if you
have three bookmarks, you can pass 0, 1, 2 to this signal to switch to each of them, respectively.
The default binding for this signal is `Alt + 1`, `Alt + 2`, etc. until `Alt + 0`. Note that in the default binding, that `Alt + 1` is actually defined to switch to the bookmark at index 0, and so on successively; `Alt + 0` is defined to switch to the bookmark at index 10.
| bookmark_index |
the number of the bookmark to switch to |