How to make the WebIDE pop-up moveable / draggable and custom sized?

Sizing I found and it is easy: create a CSS class and hook it to the id. For example:

Dynamic style additions (will move into a .css file when done...):

  // ...until CSS is settled this will go into (a) *.css* file  
  function supplementCSS()  {
    = '<style type="text/css">'
    + '#imageItemList { width:620px; }'
   // ...more style definitions
    + '</style>'
    ;
    $(css).appendTo("head");
  }

Popup code that uses this style:

      Espruino.Core.App.openPopup({
        position: "relative",
        title: "Assign item to clicked image position",
        id: "imageItemList",
        contents: html
      });

@Gordon, what are - if there are - the specific guide lines how to name classes for plug-ins? ...multi level class definitions? ...what are the reserved prefixes?

it was part of trying to make the IDE more simple and friendly to new users.

Well understood and supported.