Combine multiple "FOLDERS" (not files)

Have you tried the get data from Folders option?  There is a good explanation here http://powerbi.tips/2016/06/loading-data-from-folder/

This solution assumes that the multiple folders are all subfolders in the same parent folder.

But what about a different scenario where there are multiple folders that are not all subfolders in same parent folder?

Can the Source have OR statements? something like ..

Source = Folder.Files("C:\Users\xxxxxx\myDocuments\folder2" OR "C:\Users\xxxxxx\Desktop\folder2"),

I haven't been able to make anything work or see any other possible solutions by searching.

The solution is relatively simple, just requires an extra step or two. 

Power query does most of the hard work for you by using the 'Get data from folders' option, but you need to add to some extra steps to extract from multiple folders. 

Here's the code. I've given a full explanation below though.

let
    Paths = {{"C:\Users\ME\Desktop\Folder"}, {"C:\Users\ME\Documents\Folder 2"}},
    #"Converted to Table" = Table.FromList(Paths, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    #"Extracted Values" = Table.TransformColumns(#"Converted to Table", {"Column1", each Text.Combine(List.Transform(_, Text.From)), type text}),
    #"Added Custom" = Table.AddColumn(#"Extracted Values", "Custom", each Folder.Files([Column1])),
    #"Expanded Custom" = Table.ExpandTableColumn(#"Added Custom", "Custom", {"Content", "Name", "Extension", "Date accessed", "Date modified", "Date created", "Attributes", "Folder Path"}, {"Content", "Name", "Extension", "Date accessed", "Date modified", "Date created", "Attributes", "Folder Path"}),
    #"Filtered Hidden Files1" = Table.SelectRows(#"Expanded Custom", each [Attributes]?[Hidden]? <> true),
    #"Invoke Custom Function1" = Table.AddColumn(#"Filtered Hidden Files1", "Transform File", each #"Transform File"([Content])),
    #"Renamed Columns1" = Table.RenameColumns(#"Invoke Custom Function1", {"Name", "Source.Name"}),
    #"Removed Other Columns1" = Table.SelectColumns(#"Renamed Columns1", {"Source.Name", "Transform File"}),
    #"Expanded Table Column1" = Table.ExpandTableColumn(#"Removed Other Columns1", "Transform File", Table.ColumnNames(#"Transform File"(#"Sample File"))),
    #"Changed Type" = Table.TransformColumnTypes(#"Expanded Table Column1",{{"Source.Name", type text}})
in
    #"Changed Type"

First, just extract some data from one folder using Power Query's built in option. 
in this case i've got a folder on my desktop imaginatively called 'Folder' with 3 files in it, CSV1, CSV2, CSV3

at this point Power query has included in the code a line that specifies the folder path we'd given it 

and then applied a number of steps to the files to bring them into a single table. 

Power query generated code from Import Folder

We need to replace this folder path with multiple folders.

Personally, I've used a list. You can do this other ways. But you need to get a table with a single column of all your folder paths, this is before the code written by Power query.

Create table with single column from a list of folder paths

and then all we need to do is replace the 'Source' line with an expansion of the table with the method Folder.Files
First step, add a column with the function Folder.Files([Column1])

Add column Folder.Files

Then expand all the columns from this.

Expand all

Remove the original 'Source' using the query settings & the whole thing should work.