Hi,
Make sure, that the cursor is in the text area. Then try ctrl-Enter. If it doesn't work check your plugins, if one of them may change the keyboard handling.
There is no shortcut to delete a tiddler. We try to avoid loosing data accidentally. At the moment there is no mechanism, that selects tiddlers in the story river. If several tiddlers are open, you can't be sure which one will be deleted.
-m