Example of how to set EE events to have a default venue when created.

tw_ee_set_default_event_venue.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

add_filter('FHEE__EE_Form_Input_Base___construct__input_args', 'tw_ee_set_default_event_venue', 10, 2);
function tw_ee_set_default_event_venue( $input_args, $input_obj) {
    if( 
        !empty($input_args['html_name']) 
        && $input_args['html_name'] === 'venue_id'
        && $input_obj instanceof EE_Select_Input
    ) {
        // If no venue has been set on the event, set a default venue to use.
        if( $input_args['default'] == 0 ) {
            $input_args['default'] = '235';
        }
        return $input_args;
    }
}