How can I create BOM in assembly only for Tool Box Fasteners

Not a direct way but you can suppress all other components and then create a BOM for fasteners. Use advance component selection in assembly and select all toolbox part. Then right click on screen and select "invert selection". This would select all component expect toolbox part. Then you can again right click and suppress them, leaving you with toolbox parts only. Now make the BOM.

For a similar need, I've raised the idea for Fasteners only BOM.

Another method to consider:

Place a complete BOM on drawing

Add column with Custom Property "IsFastener"

Sort BOM by the IsFastener column

Hide all rows that are not fasteners

Save this format as a BOM Template for future use.