Hi Pavel,
I have the same problem. I have supplier in EUR but my default Store is CHF. I don't use plugin currency selector. When I want to edit my purchase price the only option is CHF which would not help to generate a proper PO, as my suppliers would not understand a purchase in CHF. I really need this feature very soon... Then I don't really understand why you allow user to set a different currency, and just no set the default currency. By the way for a same product I could have different supplier in EUR and in CHF with different purchase pricing. Does the plugin could manage this?
Thank you very much for your help and you great project!
Very warm regards and my best wishes for 2019.