How to delete an element with mandatory field(s)?

There are mandatory fields in different element like in Related Activity, you must enter/select TYPE OF RELATIONSHIP and ACTIVITY IDENTIFIER.

However if you decide not to include that element in your activity, you would click delete icon. If you have multiple elements (after Add More) and you include at-least one element and save, then it works.

However if you remove the last element and try to save it, you would get an error.

You need to remove the entire element, go to View Activity and if you hover over that element that you want to remove, then you would see x icon.

Click that x icon and the element would be removed from your activity.