Parsing through list values in a parameter

Hi asubr, I think you are asking if Power Query parameter could include multiple selections.  The answer is yes and no.  Power Query parameters do not allow a list of values as a parameter value.  However, you can consider using the parameter as text string that contains the following examples:

FileName = "2015"

FileName = "2015, 2016"

FileName - "2015, 2016, 2017"

The trick is to convert the Text string into a Table with rows.

let
    Source = #table(type table[FileName=text], { {FileName} }),
    #"Split Column by Delimiter" = Table.ExpandListColumn(Table.TransformColumns(Source, {{"FileName", Splitter.SplitTextByDelimiter(",", QuoteStyle.Csv), let itemType = (type nullable text) meta [Serialized.Text = true] in type {itemType}}}), "FileName"),
    #"Trimmed Text" = Table.TransformColumns(#"Split Column by Delimiter",{{"FileName", Text.Trim, type text}})
in
    #"Trimmed Text"

You now need to add the custom function to this table using this modified function

(FileName as text) as table => 
let
  FullName = "File Name" & FileName & ".csv",
  //Please refer to the SharePoint Site rather than the Folder Path.
  Source = SharePoint.Files(#"SharePoint Site", [ApiVersion = 15]),
  //I have added a Text Contains to select the folder.  You could use the full path or end with instead.
  #"Get File" = Table.SelectRows(Source, each [Name] = FullName and Text.Contains( [FolderPath] , "Folder Path" ) ),
  #"Get Csv" = #"Get File"{0}[Content],
  #"Imported CSV" = Csv.Document(#"Get Csv", [Delimiter = "|", Columns = 7, QuoteStyle = QuoteStyle.None]),
  #"Promoted headers" = Table.PromoteHeaders(#"Imported CSV", [PromoteAllScalars = true])
in
  #"Promoted headers"