Hello @M Sheeโ ,
In a drop down you can select a value from a list of provided values, not type the values in.
What you might be interested in is a combobox - It is combination of text and dropdown. It allows to select a value from a provided list or input one in the text box.
Please refer to the documentation here https://docs.databricks.com/notebooks/widgets.html#databricks-widget-types
You can also check the following dbutils.widgets.help("dropdown") for details
Thanks!