For your information, I used this “technique” in my tax return this year, it worked perfectly! Although the Canton of Vaud only deducted the sum of 55 CHF from the 114 CHF of VT witholdings dividends. This 55 CHF was reduced from my taxes. That’s still one less thing to pay.
As for the tax statement, I used this custom model: Interactive Brokers for dummies - #413 by xerox5003
I didn’t have any problems, so in the end, you can put all your positions (US stocks, CH, EUR, US ETF, CH, etc.) in this section and the authority will take everything into account. No need to mention European positions in another section, as I had done for my iShare SPI. They corrected by saying that this ETF was already declared in the DA-1 section.