text: Title: Support creating assigned variable name based on another variable like `${${var}} =    Keyword`
  Body: Apparently, it is not possible do return values into nested variables in RF, for cases like:
  
  ```
  ${x${y}} =    Keyword
  ${x}[a] =    Keyword
  ```
  
  These can be quite handy aswell while using FOR loops, to populate values inside, like:
  
  ```
  FOR    ${INDEX}    IN RANGE    1    4
          Keyword1    ${user${INDEX}-email}    ${user${INDEX}-fullname}    gender=${INDEX}
          ${short-id-${INDEX}}    API - Get User ID    ${user${INDEX}-fullname}
  END
  ```