Вероятно, можно сделать так:
let
Source = Excel.CurrentWorkbook(){[Name="Таблица1"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Что есть", type text}}),
replace = Text.Replace(
Text.Replace(
Text.Replace(
Text.Replace(Text.Combine(Source[Что есть],","),"C","")
,"-","..")
,",,",",")
," ",""),
split = Text.Split(replace,","),
res = List.Transform(List.Union(List.Transform(split, each
if Text.Contains(_,"..") then List.Numbers(
Number.FromText(Text.Split(_,".."){0}),
Number.FromText(Text.Split(_,".."){1}) - Number.FromText(Text.Split(_,".."){0}) + 1)
else {_})
), each "C" & Text.From(_))
in
res