Global planner IDs should be hyperlinks in their own right. They are of the form

plan://id-number or
plan://id-number/page,page,page,page

But then how do we define anchors and references?

Reference: plan:///id-number or plan:///id-number/page,page,page,page (note: triple-slashes)

Or maybe plan:id-number[/page,page,page] for the anchor. Double-slashes will not be updated.

I want IDs because I’d like to e able to update notes in case of
typos.

Then this is no longer emacs-wiki-id, but really just planner-id.

Yikes, I will so break the existing planner-id support with
this… There must be a better way. At the very least, I should offer
a conversion function.

../../notebook/emacs/emacs-wiki/emacs-wiki-id.el