How to copy the full path to the file in the current editor?

Right-click in the current editor, then choose Copy Full Path.

You can also assign it a shortcut: go to Window ‣ Preferences ‣ General ‣ Keys (or press twice Ctrl+Shift+L) and assign a shortcut to Copy Full Path. It’s a global shortcut, you can call it from anywhere but only the active editor’s input will be considered (or the current selection in the navigator if you call it when the navigator view is active e.g. after you select a file).