Hello
I think you can map the process using 101 as an intramaterial. You can post a goods receipt of this material on stock, adding it with a negative sign on the BOM of 102. Then you will include it again with a positive sign and refer it on a subsequent operation. That way, you will be able to see it on stock. In this case, you will only create one BOM for material 102 with all the components.
BR
Caetano