Hello Priya,

As you are using EnableCustomValues="False", the input field for the WebDropDown will not allow any editing. This is the reason why it is not possible to edit/add/delete – as the input could only march one of the existing in the WDD items values. This is by design and the expected functionality.

However, in order to make this more user friendly, I suggest adding the EnableAutoCompleteFirstMatch="true" property. Using it will ensure the input will be matched to the first available and it will ease the user selecting/inputting correct value. Please notice it is always possible to delete the current value like using some of the following approaches:

1 – Select all of the current input using the mouse and delete using delete btn or cut
2 – press ctr+a to select all input, while the focus is in the WDD input field and press delete or ctr+x (cut)

I am attaching a runnable code sample illustrating the suggested approach. Please let me know if you require further details.