In ABAP projects, you can only add packages (not other types of development objects) to your favorites list.
As an ABAP developer, you will generally work with a limited selection of ABAP packages. Therefore, it is appropriate to include in your favorites list for your ABAP project exactly those packages that are relevant for your work. The packages listed there remain assigned to the ABAP project on a permanent basis.
There are following possibilities to add or remove packages to/from the list of favorites: