1. Upload your new template to test blog. Help
  2. Go to Dashboard. Click to Layout of current blog (not new test blog) --> Edit HTML --> search for: <div id='sidebar'> copy all widget code between <div id='sidebar'> to </div>
  3. Now Go again to Dashboard. Click Layout (at new test blog) --> edit HTML --> search for <div id='sidebar'> --> paste all widget code that you have copied. Put it between <div id='sidebar'> too
  4. Save
  5. Download and save full template of test blog
  6. Upload to your current blog layout, and you get new layout without deleting widget