You can set the is_Hidded property of the field in the database to 1, which will do the job. Then go to the dynamic module, open the type and resave it, which will cause a restart of the module and the change should get applied. I have attached an image for your convenience. The property is in the sf_mb_dynamic_module_field table. To disable the field for the front-end, you will need to manually remove it from the template of the dynamic module widget or remove it from the configurations. However, if you choose the second approach, the field will be written again in the configurations, every time you update the module(resave it), so maybe the first approach is better for you.
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