For custom commands it is useful to select an earlier command and have it copied
to the prompt for further editing. This can be done by hitting 'e' now.
For other types of suggestion panels we don't enable this behavior, as you can't
create arbitrary new items there that don't already exist as a suggestion.
In the custom commands panel you can now tab to the suggestions and hit 'd' to
delete items from there. Useful if you mistyped a command and don't want it to
appear in your history any more.
