Merge Mode

I have multiple collections. How do I merge them so I see them in all books instead of switching to each collection? I still want to keep the names of each collections seperate.

I am afraid that is not available.

Collections are meant to be completely separate databases.
As soon as you feel the need to browse or search all of them in one place, then that is a good indication that it would be better to use ONE collection, then maybe use Tags to separate the parts into folders.