@Koepel Thank you very much! You save me a lot of time!
[This shifter is a therefore 1 channel one and not a 2 channels one, aka it can only command one sensor mounted on I2C. Very misleading name: one wire I2C does not make any sense, it shall be at least "one pair of channels" or similar, in my opinion.]
I dare to stress again that you helped me very much.
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I hope I can power the shifter from my Arduino Nano. The Nano description said that the 3.3 V output is not available when powered on sources other than on USB. However, I measured the 3.3. V of the Nano (powered via 5V - regulated) and it does output 3.3 V (3.43 V to be precise).