Could I edit keywords fields (Description, Key or Metadata) using Experience Manager?
We are using Tridon 2013 SP1.
Strictly speaking, you cannot edit a Keyword itself via Experience Manager, since it only exposes a way to edit content fields.
If you have a Keyword field in your Component and the value from that is displayed, you can change the value (to another Keyword). If you also have rights on the Category to add new Keywords, you have the option to add a new Keyword via Experience Manager. For that new Keyword, you will get to see all options, so you can set Description, Key and Metadata. But you can only do that while creating this Keyword.
But from the 2013 SP1 Experience Manager view, you do have the option to Switch directly to the Content Explorer interface (see the slide-out navigation). This basically gives you the option to navigate to the Category and keywords you want to edit. When done, you can simply chose the "Editing Site" again from the slide-out navigation and you are back in Experience Manager (on the page you were before).