Ability to create URL redirects for deleted collections
Alma offers institutions the ability to create collections to facilitate discovery and access to groups of related resources. In addition to being displayed on the Collections Lobby page, collections can be made accessible via direct links on websites, research guides, or course syllabi. However, when a collection is deleted, any links or bookmarks to that collection are broken. To avoid this, customers should have the ability to configure redirects for collection page URLs that can be used to route visitors to another page.
Related documentation:

-
Peta Hopkins commented
-
Paul Harding commented
It should also be possible to configure redirects for collections when migrating to VE in the same way that you can for other links in the deep link redirect mapping table.
-
Manu_Schwendener commented
Not what you are asking for, but related:
For a 404 page, see also https://ideas.exlibrisgroup.com/forums/308176-primo/suggestions/44056683-allow-custom-error-pages-if-view-code-does-not-exi