I can't sort items out of group

[Nekiess]

I have a table like the one below, I have items outside groups and 1 group, I can get items that are inside group and put outside this group but I can't get items and add to group, how to add items to group? . . The HTML: .

A Column
A Item 1
A Item 2
A Item 3
A Item 4
A Item 5 A Item 5.1 A Item 5.2 A Item 5.3 A Item 5.4
A Item 6

. . . . The JavaScript

. .