Splitting of values in a JSON array
Try this:
var input = "['[\"~:bbl:P5085\",\"~:cosco:NoTag\"]']";
var BBLs_List = JArray.Parse(input)
.SelectMany(m => JArray.Parse(m.ToString()))
.Select(s => s.ToString().Split(":"))
.Where(w => w[1] == "bbl")
.Select(s => s[2])
.ToList();