How to set up “localhost” document root as Mac’s “Sites” folder with MAMP PRO 4

The default MAMP's localhost document root is /Applications/MAMP/htdocs and I want to point it on my /Users/Me/Sites/ folder.

I can do easily with MAMP PRO GUI but it's not working after I restarted servers and it's showing me a red arrow (as an invalid destination):

I tried some solutions like:

• Change default Apache port to 8888
• Change default web user to me
• Do an alias from MAMP htdocs folder to Sites folder
• Do a symbolic link from MAMP htdocs folder to Sites folder
• Try to set Sites folder owner (only) to me and group to Sites (but doesn't seem not work)
• Set Sites permissions to 777, 755 and 750
• Add an index.php file inside
• Creating a new host

But MAMP still doesn't accept my Sites folder as document root!
I tried with websites sub-folders inside Sites or with other Mac's personal folders like Music, Pictures, Downloads or my own home and they are working! Only Documents or Desktop folders don't work either.

It's seems a permission issue, but I don't know how to resolve it. Does it because Sites folder is used by other macOS apps or services?

Edit (27/07/2017): I opened an issue on official MAMP bugtracker: http://bugs.mamp.info/view.php?id=5945

Edit 2 (10/01/2018): From an official MAMP bugtracker administrator: "~/Sites will be allowed starting v4.3." (adb – 04.12.2017)

Edit 3 (07/02/2018): New MAMP v4.3 (released 24/01/2018) allows "~/Sites" as localhost root folder, watch my answer below.