While working with Mappings, you can hide all datastore unused fields to improve readability of the overall Mapping.

Click on the datastore on which you want to hide fields, and then on the little top eye button:

selective display

You can then uncheck all unused fields you don't want to see in Mapping and click on apply.

A button is available to automatically uncheck all unused fields.

unselect unused fields

Finally, after having hidden all unused fields on all datastores, our initial Mapping will be as follow:

mapping final