It seems technically a Wise account gives you many (virtual) accounts. What’s the best way to declare these? As one account where you convert all the currencies to CHF or as individual accounts, relying on the online tax software to convert the currencies? The latter seems to be a pain.
I don’t think this matters as long as the total in CHF is correct.
(Also they probably don’t care unless you have large amount of money, I assume more than what you’d use as cash)
The accountant declares it as a single line item of the total converted CHF amount at 31.12.
I’ve always passed to the accountant the total for each of the open accounts at the 31.12, CHF and EUR last time, then they deal with it.