Sometimes, you may want to take control over index fields generated from data model
properties or add new fields to store specific elements of your corpus.
This can be done by editing or adding fields in the Data Model > Advanced
Schema tab.
For example, you can add binary retrievable fields to store binary data in the index. This
can be useful if you want a dedicated thumbnail or preview generation and make it available
directly inside the document. This also allows you to optimize the index storage.