Is it possible to add the functionality for the constant fiat offer? Let’s say I want to buy BTC, and I would like to spend $100 (or EUR, or whatever). May I set it in such a way, that my offer is always for $100, and it is the amount of BTC which is being adjusted?
No, this is not possible. I think it is technically a little difficult to achieve as would require a variable locked trade amount / security deposit.
I was wondering the same, keeping a money order buy under an amount.
You can use a fixed price offer for that (not % based). Using the deactivation trigger price might help with your needs as well.