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Good morning Sundew, first thank you for giving such detailed explanations!
Sure, living room is not very helpful:D, I've forgotten to say that I live in Germany, in the south of Rheinland-Pfalz.
And sorry, that I can not show the necessary details (have to buy a new camera ;-)), but the tip of the abdomen of this chrysotoxum you can see at the first picture of it, I posted the 30.06.2020. Please have a look on it. The length of this syrphidae was about 12-15 mm.
I hope this added informations will help to give my chrysotoxum a name...
Have a sunny sunday and kind regards,
bubu