hey,
i was also looking for a solution to enable the swift page builder for my custom post type. luckily i know from different themes where to look. the biggest problem is to find the little piece of code where the page builder will be assigned to the post types. well i took me 10 minutes to find the right lines:
add in line 42 and 44 your custom post type:
dante/swift-framework/page-builder/builder/lib/builder.php
i know that’s not the best solution, but as long as there is no other possibility as mentions by one of the staff members, this should work till the next update.