In entries explanations and configuration, make it possible to "split"
the list in multiple sub-lists visually: a ``null`` item should just
create an empty space, not display a list item "dot"
* interaction is terrible, select is ugly but radio buttons take way too
much vertical space, no matter whether they're on the left or the
right
* may be possible to unify operations lists between chart of accounts
and entries? Not currently selected set, just the list of possible ops
