Answer
This isn't supported — Aurena's custom-tab functionality for adding another page as a tab only works with List-type content; there's no way to add a Form/Detail-type page as a custom tab bound to a parent record. Per IFS's own technical documentation on this, the correct approach when you need form/detail-style content (not a list) tied to a Custom LU is to build it as its own new custom page instead of trying to embed it as a custom tab on an existing page.