This option allows users to bypass the "publish preview" modal. Users can disable it by checking "don't show this again" in the modal, and re-enable it in the Settings Page.
This requires an accompanying change in lbry-redux. Search for "SETTINGS.ENABLE_PUBLISH_PREVIEW" in the commit message to find the commit.
In Edit Mode, the preview will not appear. Not sure if it's needed, plus there are more things to handle in Edit mode (e.g. which items are changed)