Change Parser settings doesn't work based on union array order

Attach a patch and MR.

I don't understand your issue. I tried to reproduce it in the following way:

1. Created a feed type with the HTTP Fetcher (download from url) and the CSV parser.
2. Mapped to "title" to node title and "body" to the body field.
3. Created a feed, I noticed that delimiter was set to , (comma), changed it to ; (semicolon)
4. Imported the following source:
   

   title;body
   Foo;Bar
   
   

And the content imported fine.

So perhaps there's a specific plugin or module that disrupts the process?