For your expected dataset, did you use actual code to create that, or is it just a graphic or some other "fake". If I could see the actual structure of that dataset, it would be easier. But anyway, in the meantime, this is close:
d1 = Dataset[{<|"Date" -> DateObject[{2024, 1, 10}]|>,
<|"Collection-area" -> Quantity[3, ("Centimeters")^2]|>,
<|"Integration Time" -> Quantity[2.1, "Seconds"]|>}];
d2 = Dataset[{<|"\[Lambda]" -> Quantity[195.050, "Nanometers"], "r" -> Quantity[2.9, "Watts"]|>,
<|"\[Lambda]" -> Quantity[196.000, "Nanometers"], "r" -> Quantity[2.1, "Watts"]|>,
<|"\[Lambda]" -> Quantity[196.050, "Nanometers"], "r" -> Quantity[2.6, "Watts"]|>}];
Dataset[Append[d1, Merge[d2, Dataset]]]