Hi @Sgaucher,
Importing posts and post meta should also import header and footer (as they are post type as well). But if you’re just importing blog posts then I recommend importing all kinds of posts (all post types).
As for post meta, you’ll have to match it with the ID from wp_posts
table.
Example,
This is just to demonstrate the location of the data, you may export and import them but that process could damage the existing data. I recommend using the builder’s template export/import feature. Simply save them as a template (header and footer) and go to X/PRO > Template Manager and export your saved templates and import it to your target site using the same Template Manager.
Thanks!