Two ways of structuring a long list.
First, at the top of the list, put what you think would make sensible topic names.
Then, if the list contains blocks of related entries, select them in groups and shift/drag them to the appropriate topic name.
If the list contains more scattered related entries, it might be easier to promote a topic name, mark the first entry (click to the right of the entry icon), demote then whizz down the list hitting Ctrl+T every time you find an entry to throw to that topic.
Repeat for each topic and anything that's left over will be a clue to your missing topics.
PS You could, of course, split the model window and drag and drop between the open windows.