When opening a PL/SQL package from a file in the editor window it asks if the file should be split. Answering yes, it adds the toad_file_chunk tags. If a change is made to the package and saved, when the package is re-opened it adds new toad_file_chunk tags. So, it ends up with 3 tabs.
The first tab just has toad_file_chunk.
The 2nd tab has 2 toad_file_chunk, about 5 blanks lines, and then the package spec.
The 3rd tab has 2 toad_file_chunk and the package body.