Mailster 4.0 introduces a new way to create forms. The new builder is based on the WordPress block editor and your forms created with Mailster before 4.0 need to be converted. Legacy Forms will work in the future but we decided to no longer keep them updated in favor of block forms.
It is high time to upgrade to the new block forms if you are still using shortcodes on your old newsletter homepage. This guide can assist you in migrating to the updated version.
If you click on the Block Forms menu entry you see an overview of your current existing block forms.
Mailster forms can be defined and customized via the forms page. You can add additional content via some coding by using the mailster_form filter hook.
By default Mailster forms are ajax based and you get a nice confirmation message after your users have submitted the form. If you like to redirect them to a specific page you can find this option in the form settings.