Adverb expressions such as ‘not only’, ‘not just’, and ‘not simply’ emphasize that something is true, but it is not the whole truth. These co-ordinate clauses.
In the English Grammar Profile, C2 point 92 in the category of PAST is defined:
present perfect continuous, invert the subject and affirmative auxiliary verb with ‘not only … but’ as a focusing device
but together, we started a live storytelling series we’re calling Talk Rx,