How to define a custom search index for the entries fieldtype

[Alpenverein]

If you search in the controlpanel for an entry in a collection, you can define a custom search index by defining it in the config/search.php and by defining it in the collections yaml file.
If you want to link an entry with an other one by using the entries fieldype you see a search gui which doesn't uses this index but the default one..
Is ist possible to have the same search experience for that search as well?