The online documentation addresses these issues, please refer to this for more
As for "default" actions, the documentation says:
You may define default verbs using '._DEF_.verb' definitions to handle
extensions \ that are not defined, or files that have no extension. You can
handle specific files with no extention, for instance 'Makefile', by defining
It is not clear to me why the "open" verb would affect the "edit" verb. This may
be a bug, although I have never seen it before. Please let me know if you have
any more details about it.