Just thought I would share this, as it may not be entirely obvious to everyone. To be honest, am a little embarrassed that I didn’t really discover this until now. Full disclosure: this came about after feeding the DT manual and this forum into NotebookLM, so credit to it for walking me through the options.
I was looking for an efficient way to link documents. I am not especially interested in Hookmark, although I acknowledge it does do exactly this.
Solution: Settings → Data → Custom Metadata. Hit the + button at the bottom and add a new field. Select type to Rich Text. Name it something like “Related Docs”.
Going forward, after right-clicking any document and selecting “Copy Item Link”, you can then paste it in the Related Docs field in the Inspector. The best part is that you can paste multiple doc links. Even better: click the link and it opens. Command+click and the link opens in a separate tab in the same window. This workflow moves away from the creation of a separate annotation file that just holds, for instance, links to related documents (as useful as that can be in some instances, of course).
As I say, thought I would share on the off-chance it could be helpful to someone.