Does anyone know how underlying accounts are coded/work with A/R and A/P?

Specifically, I'm interested in (finally) understanding the nuances between how the software/QB does things versus what an accountant would think and/or expect to see based on what they're trying to do. So, one example of what I'm looking for, I just made a JE to debit a legal expense and the associated ITCs to a GST account and credit another asset account since that's where the payment is ultimately coming from. Interestingly, and despite using the supplier's name in the journal entry expense account line, a bill wasn't created, nor did the expense show up in the supplier's profile (i.e., menu -> Suppliers). I had though debiting an expense account + adding a name would create a bill for that supplier you'd then need to pay bills to address (or debit A/P same name and apply that credit using the pay bills feature). What I clued into just now was/is that the current asset account used for the credit is not a bank or chequing account type in QBO which I think now is what actually drives the pay bills feature/function. Or not. I was surprised that I could not find a trace of the expense in the supplier's account after i posted it. Ugh. Hopefully somebody can make sense of this and ideally point me towards a discussion where this has already been discussed and outlined. Man. It makes me want to retake my QBO training to really nail down how the software works "under the hood" so to say. TIA for your replies and help!