If I have understood you correctly, what you are trying to do is maintain an inventory of what consumables you physically have in stock and you are transferring that to an expense account when start using that consumable say ink toner?
What I was going to suggest was using Purchase Invoice Items so that you can allocate your ink or whatever purchase to the correct expense account, but I see that doing this will prevent you from being aware of what is physically on the shelf waiting to be used. I don’t know how custom control accounts will be implemented but it sounds interesting if it will allow you to be aware of what you have on the shelf waiting to be used and I presume it will allow you to monitor how quickly you go through consumables as I presume that is the main aim.
I had a similar issue some while back when I was thinking of using Manager to track my car expenditure, not just simply to record the purchase of car tyres and shock absorbers but more to be aware of when equipment needed to be replaced so that I didn’t get shocked by huge unexpected bills for my car services.
I came to the conclusion that I should use Manager to record all my purchases from an accounting point of view and that would help me to keep track of how much I spend on the car each year, but I needed to use a different program to track lifespan of parts such as brake pads etc to be able to budget for when I next needed to replace any given item. I bought a program called Kaizen Vehicle Manager 2014 Home Edition Software and I have found it to be really good for tracking my fuel costs as well as mileage performance and putting all my vehicle invoices into the program.
Vehicle Manager Software
In short, my point is that while Manager is very good, it might be better to use Manager in conjunction with other software to accomplish your task. I doubt that Manager could do what Kaizen Vehicle Manager does without adding extensive functionalilty that is only relevant to cars! I would certainly wait and see how custom controls works before doing anything, but I just think that there are times when a dedicated program would work better than trying to get one program to do everything. Just my opinion.