Settings -> Preferences -> Language -> Tab Settings -> check "Replace by space" option.

Ref:- https://stackoverflow.com/questions/8197812/how-do-i-configure-notepad-to-use-spaces-instead-of-tabs

• Move a tab to new window
  • https://stackoverflow.com/questions/13252968/how-do-i-move-a-tab-in-notepad-to-a-new-window