I can't really grasp what you're doing with your forms but wanting to have a datasheet and cf form together is a strange request. A split form is a real thing, but that's 2 representations of the same records but having a main form view above a datasheet (or reversed). The only way I can envision this is with 3 forms - main form with 2 subforms, one ds, the other the cf but syncing them might be a challenge. Your better bet might be a main form for product data and a cf for notes. When you navigate from record to record in the main form, the subform would show the related info. I for one would put notes in their own related table and usually not append to the same note each time something is added. Doing the latter can make it quite difficult to find notes entered by a person, or on a date, for example.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.