We can't set the work parts order in a parent work in the work-work "part of" relationship (related to STYLE-69).
Example : 組曲「九尾」〜玉藻前〜照魔鏡〜殺生石 (not 殺生石〜照魔鏡〜玉藻前 as it is now reversed, based on title characters)
From MBS-3062↗

I apologize if there's already a ticket for this...

We need the ability to set the sort order for sub-works.
For example, is the sub-work, the 1st movement? the 2nd movement? etc...
This is important because not all sub-works follow the I., II., III., naming convention and there is no way to know what is their original order. (As of now, I'm adding the order in the comments (example: http://musicbrainz.org/work/f86bad98-b743-4597-aeba-8605c7dcb603)

Perhaps this should be set as an attribute when linking two works.
Ideally, there should be an AJAX UI where we could drag the new sub-work and drag it into the existing list of parts and place it in the desired position.
A simpler solution would be to attribute a number to each sub-work (attribute of the work -> part of work relationship) but MB would need to be smart and not allow two sub-works to have the same number (it should automatically move them back if a sub-work is added in the middle.