You can define default types for links and destinations, which will be
used when you do not specify a type in
\hlstart or
\hldest. Similarly, you can define default values for the
options; the default value for an option is used when you do not set the
option in the argument to \hlstart or \hldest.
The parameters for implicit links and destinations can be customized by setting the “group” types and options. When not set, the defaults are used.
All these settings are local to the current (TeX) group, so if
you want to set an option temporarily, you can do so inside a
\begingroup...\endgroup block; when the group ends, the
previous settings are restored.