Add option to Disable or Hide the prepopulated fields in the entity form

FYI, this can be achieved with the help of other modules in conjunction with Entity Prepopulate:

1. ECA with the ECA Form submodule: you need to react to the event "After build form" with action "Form field: set as disabled"
2. Conditional_fields module, only if you can react on another field on the same entity form: in Manage Dependencies select your Target field, the Controller field, set target as Disabled when control is Filled.

As workaround you can use →

I am using field group > html element and creates css "hide_prepoulate" like :

hide_prepoulate {display:none;}

I will add field group called "admin" or so and add fields unders this group which have to be hidden (not visible for user) and add to Extra CSS classes option "hide_prepoulate".