I don't think there is a way to have a single instance generate multiple line items in a BOM. To do this, I have a single generic schematic library part that has a symbol that is just a text note.
Here is an example. I do this for various parts such as the bare PCB itself, adhesives, assy procedures, silpads, heat sinks, fasteners, etc.
The schematic symbol looks like the following:
This is just a text frame with a note and then the "Apply to...." text is a parameter that I can change. It would appear on the schematic as a note but it generates a BOM item. Also, if I include the parameter in the BOM then the text appears there. The parameter I use for the notes I call "Component Note1" and I put special notes or extra value information there that I want to appear on the BOM.
You will see that I made the Type dropbox be the mechanical type. Here is a shot of the library part that puts the bare PCB p/n into the BOM.
These end up appearing on the schematic something like this.....
I didn't make the Default Designator visible but if you did you could make ordered numbered notes. I typically just bunch up the various mechanical only parts like this on a top sheet or with the fiducials or mounting holes or something.