It is possible add multiple records from an Insert form. You can either add a blank record by pressing the "Add another record" link at the bottom of the form, or copy an existing record by pressing the appropriate button at the right top corner of a subform. It is also possible to create multiple subforms at a time by selecting the appropriate item in the button's "Add new" drop-down menu.

Click the caret on the right of the 'Add new' button and select an option to see this feature in action. Lazy users can simply click one of ready-to-use links below: