I have found a (cumbersome) solution to this using Xfce. Its Thunar file manager does implement type-ahead, so whenever I need to open a file that is saved in some deeply-nested folder, I open Thunar (using a custom shortcut, Ctrl+Alt+E) and quickly navigate to the file using type-ahead and press Ctr+L to copy its full path to the clipboard, then I switch to my app and paste the address.

For complex paths, I found that this is the quickest way to open the file I want.