http://tiddlywiki.org/wiki/Persistent_Options
> - change of theme to 'bleach'
> - use tab to move between fields rather than enter a tab space
As per the article above, use the following:
config.options.txtTheme = "bleach";
config.options.chkInsertTabs = false;
If you install the codemirror plugins to extend the editor function I belive there is a way to insert tabs including automaticaly keeping indents.
Regards
Tony