Recommend way to get meta_value to email

I have plugin that fills meta_value for order. (wp_postmeta table)

meta_key is “_woo_posti_shipping_tracking_code” and code itself is saved in meta_value field (string).

I want to use this value on my emails. My question is:

What is correct way to get this working? I wish that it would be possible to use ANY meta_value (by meta_key) in email templates, but if it is not possible and there is working plugin, that would work fine too.

Maybe best way would be plugin that creates shortcut (like {_woo_posti_shipping_tracking_code}) from ANY meta_key and it would be usable anywhere (order (info) pages, emails, etc…).

I’m ready to pay something for plugin like that.