Hi Mobo,
we do have easy way to update the pdf file within a Mindmap Notebook. And it can be used to do what you describe to import the newer pdf with edited TOC.
As the pic. shows, when you directly delete the old pdf file but keep the notebook file，the study interface will shows like blank pdf.
Then click ‘manage’.
There is a button like plug. Once old pdf’s plug out , the new pdf could compulsorily plug in with existed note.If your new pdf is the same book，the file within notebook will be updated.
Finally, TOC editor need some time to look for a pdf tools solution. And if I have news about it I will mention it to you here.