Combobox (searchable select list) is a great replacement to the standard select list and autocomplete. It removes the limitation of APEX autocomplete item which can have only one column for display and return. This is easy to configure and easy to use that enables you to add a new value to the drop down list on the fly.

A case in-sensitive search is performed with the entered value for both Lazy Loading and Non Lazy Load. 

Plugin options:

Lazy Loading:  If set to yes, the matching values will be read from the database each time the user types a character. If set to no, all values will be read only once when the page is rendered..

Allow Add New: Chose yes if you want to allow the user to add new values to the list using below PL/SQL Block (Only Available if Lazy Loading is set to Yes)

PL/SQL Code for Add New: Enter the PL/SQL Function Body to populate the new value into database table returning its ID (Only Available if Allow Add New is set to Yes)

Set Value of Combobox Using below syntax - JavaScript/Jquery:

$('#PX_ITEM_NAME').vcCombobox('SetValue',<<VALUE>>);

For Example:

$('#P4_TEST').vcCombobox('SetValue',9999);