Answer
Aurena doesn't support attaching a separate page as a 'tab' onto an existing screen the way EE's tab-based customization works — this is a genuine architectural difference covered in IFS's technical documentation's Configuration Upgrade Path section (the IEE-to-Aurena migration guidance). Instead, create a genuinely new Custom Page for that Custom LU, using the Projection you've already built, rather than trying to attach it as a tab to the existing CRM screen. IFS's technical documentation on generating custom pages for a specific entity/Custom LU in Aurena covers the actual page-creation steps for this new-page approach.