I notice that there are currently no pages about how to create a collaboration work...
Where should I add the work? How to notate the work such that it shows collaboration in respective composes' pages?
You just need to put the "Collab" template at the top, and the "CollabCat" categories at the bottom. You can choose any of the composers involved for the main entry of the work, and this method will automatically generate links from the category pages of the others.