Characters item order and "Sub-characters"

[FastusNumen]

I would like the possibility to move the characters the same way I do with World items, while still maintaining the Main, Secondary, and Minor classifications. There are already similar issues for plot order, the #1063 and #1232 issue.

I'd also like to say that given the possibility to add a "Sub-character" like how you can drag a World item under another. This, I believe, could solve what I asked in this issue, #1230, allowing us to give different personalities and or details based on the timeline of a character. For example, I could create a "Fastus" character, and add under it a "Fastus Age 11" character and a "Fastus Age 25" character. Or split personalities.

It would maybe be easier to manage than creating a new tab as I proposed in issue #1230.