Agelong Tree allows to save a part of the family tree into a separate file.

First, tick the filter to remove all unnecessary persons. For example, use Present in tree filter: build a tree with all the required persons, fold the branches with unrequired persons, then tick Present in tree filter.

Second, go to the menu File –Save filtered as and give the new file a name:

The new file will contain all persons that were present in the Persons table at the moment of saving, and all objects like events, documents etc that are connected to the persons.