Unable to set permissions for custom role to see Add Media button on a CRED form

Symptoms

Custom role cannot see the Add Media button of a WYSIWYG field on a CRED form.

Workaround

This is an issue in WordPress core, as Add Media button requires edit posts capability to work properly.

In order a custom role to be able to see the Add Media button, you need to enable for this role:

• upload_files capability
• edit own permission for posts