Hey @aleakos — thanks for posting!
You can use this in a Javascript query to clear the multi select:
multiselect1.setValue([])
The default empty state for multi select components is an empty array, so I prefer to set it to that when clearing the component’s value. You could also set it to null with multiselect3.setValue(null) if you prefer.
You can trigger this when closing the modal, via a button, after form submit, or any other way you choose.