I use WinSCP as file manager and Eclipse as external editor.
In this case files opened by ftp have path "c:\DaS\User\ and so on..." and not conside as part of project.
On it Eclipse not use for this files code completion an other features.
But if i open file as "\RSE\Local\c\DaS\User and so on..." file conside as part of project "RSE"

Can you please tell me, what would you use these for?

Now in settings for external editors substitute !.! and replace to full path to file.
It is possible add more settings? For example
!\ - Path to file
!-! - File name without path
!: - File disc