Hello TeilzeitLegende, welcome :-)
I have not tested them, but listed in the API there are the following functions:
BuyStoreItem(number entryIndex, number quantity)
GetNumStoreItems()
GetStoreItemLink(number entryIndex, number LinkStyle linkStyle)
So you should be able to iterate over all the items in a store and buy the ones you need.
https://wiki.esoui.com/API
https://wiki.esoui.com/APIVersion