Insert options are a way of controlling the types of items that users can create under existing items. By default, insert options are inherited from the standard values of the data template of the parent item. However, sometimes it may be necessary to override the insert options for a specific item, for example, to allow more flexibility or to enforce a certain structure. In that case, setting the insert options on the specific item will add those options to the list of effective insert options, along with the ones inherited from the standard values. This way, Content Authors can insert items under the specific item in addition to what is included with the item’s standard values. Note that setting the insert options on the specific item will not replace the inherited ones, unless the insert options are empty, in which case the effective insert options will be empty as well. References:

Insert options

Assign or copy insert options

Assign standard insert options