There isn't a default field for the parent term of the current term. You can use some WordPress functions to get the parent term name and permalink. For example:
{% set current_term = mb.get_term_by( 'id', term.id, 'category' ) %}
{% set parent_term = mb.get_term_by( 'id', current_term.parent, 'category' ) %}
Parent term name: {{ parent_term.name }}
<br>
Parent term permalink: {{ mb.get_term_link( parent_term, 'category' ) }}
For future reference, here is my finished MB views code:
{% set current_term = mb.get_term_by( 'id', term.id, 'category' ) %}
{# Check to see if the current term has a parent #}
{% if current_term.parent %}
{% set parent_term = mb.get_term_by( 'id', current_term.parent, 'category' ) %}
<div>
<a href="{{ mb.get_term_link( parent_term, 'category' ) }}">
All posts of <span>{{ parent_term.name }}</span>
</a>
</div>
{% endif %}
.
