You can override the template snippets/add_dataset.html
if you just want to have multiple add buttons.
Here is what you can do (tested on CKAN 2.8.3):
{# Adds 'Add Dataset' button #}
{% set dataset_type = dataset_type if dataset_type else 'dataset' %}
{#
{% if group %}
{% link_for _('Add Dataset'), controller='package', action='new', group=group, class_='btn btn-primary', icon='plus-square' %}
{% else %}
{% link_for _('Add ' + dataset_type.title()), controller='package', action='new', named_route=dataset_type + '_new', class_='btn btn-primary', icon='plus-square' %}
{% endif %}
#}
{# Custom add buttons #}
{% for type in ('dataset', 'state') %}
{% if group %}
{% link_for _('Add ' + type.title()), controller='package', action='new', named_route=type + '_new', group=group, class_='btn btn-primary', icon='plus-square' %}
{% else %}
{% link_for _('Add ' + type.title()), controller='package', action='new', named_route=type + '_new', class_='btn btn-primary', icon='plus-square' %}
{% endif %}
{% endfor %}
Otherwise if you want to have a tab for the new dataset type, you should extend the header.html
template (see block header_site_navigation_tabs
).