Currently, "Find All" searches all files, if "Search All Documents" is enabled, and only the current document if it is disabled. There could be a third mode, which uses the documents listed in one of the panes, for example a "Find Results" pane, the "Bookmarks" pane or the "Breakpoints" pane.
The user would change the "Search in..." mode from "All Documents" or "Current Document" to "Documents listed in...", and then select "Bookmarks", "Breakpoints", or "Find: foo" (a currently open "Find Results" pane).
Example: The user searched for "foo" in all documents and found the following matches.
File A.java
line 10
line 20
File C.java
line 30
Now the user starts a search for "bar" and sets "Search in..." to "Documents listed in...", and in the drop-down menu that appears then selects "Find: foo". The search is now limited to the files A.java and C.java.