Interesting workflow!
but it doesn’t work as the reference: is not recognize by Obsidian as metadata since it’s not a note but a block in a note
Right, reference: is not a property, so you can’t search for it using the property syntax.
Properties are the metadata of the file in between two such lines: --- at the top of the file. See the help docs on Properties.
You could try adding a #cited tag when you cite a highlight. Then search like so line:(#introduction #general -#cited)
Here’s a demo:
As you can see, this can correctly identify the highlights with the right tags, which don’t have the #cited tag. Of course, this requires you to actually add this tag, whereas your proposed method simply required you to add a block-id.
You can actually get the same simplicity with this query line:(#introduction #general -^), as long as the assumption holds that only highlights with block-ids will contain the ^ symbol.
For simplicity’s sake, I assumed you would format your highlights as a list, like I do in my template. This simplifies querying.
The reason I use line: and not tag:#introduction -tag:#cited is because for some reason, the latter doesn’t work, as reported here.