Inventory or working materials?

I don't think it really matters in your case.

If you are a trader, selling something on the market or something like that, then trade goods are important to the tax authorities. They want to know what you have bought and whether you have officially sold everything.I would perhaps record the ink and aftercare ointment as trade goods, but not everything else immediately. But inventory (i.e. stock list) is only at the end of the year, you know?

You record everything during the year as 'goods' (i.e. trade goods), at least what you want/need to record as trade goods. At the end of the year, somewhere around 31 December, you will see what you still have in stock, count it, and that is your inventory.

But you only have to do this once in a year, somewhere around 31/12.

Let me know if you have any questions! ;)