I'm currently using an org-file to organise absolutely everything. That includes personal stuff, work stuff, etc.
I'd like to separate a branch so that I can take it to the office with me and leave other (personal) branches aside.
Now, normally, I could split my org-file in two, add a link from one to the other, and add both to the agenda search list.
However, I'm using the sparse tress in the normal file buffer (not agenda) a lot, to get a 50K view of everything I'm tracking, including both personal and work stuff. I'm actually exporting the resulting tree to a PDF (whole buffer, only visible parts after filtering), and evaluating it carefully. This feature would not work if I split the files, unless I can somehow make org-mode understand that a separate file is meant to be treated as a subtree.
Is there any way to do this?
EDIT: Clarifies question