Ability to change times of chapter tracks by user-defined amount

[natefarious]

Currently it's possible to modify the timestamp of chapters in an MP4 file manually and individually (one at a time), but it would be great to be able to select more than one chapter at at once and then apply a positive or negative offset (change) to that selection. I currently work around this by exporting chapters, working with them in another program, and then re-importing them but that is a frustrating amount of extra steps for something that would be great to be able to do in Subler itself.