Split features in automated vs own code

Is it possible to have the features split by the automated code and the code we have written by ourself?

Here is an example of how I see it:
http://postimage.org/image/4nrsha01v/

Just like in your example: the accented Dutch ij
http://glyphsapp.com/blog/localize-your-font-accented-dutch-ij/
Sometimes we have to add the code ourselves. But when there is some code manually added, it is impossible to update the automated code after it is manually edited…

Oh, and the box below is for notations I think?
I don’t dare to use it, because it is not clear.
A grey text explaining its function would also be nice I think…

Added a description for the notes field. Thanks for the suggestion.

The custom feature part is indeed a problem. But not as easy as it looks. In the case of the local feature, the ij substitution has to be in the middle of the feature (if you have some none latin substitutions). So just adding it at the bottom would not help.

I will think about it.