The specific properties applicable to the Combo Box control are:
Content: Lets you specify the initial contents of the combo box control. Each value you enter (one per line) will appear in the drop-down list. You can also manipulate the contents of the combo box from your script.
Sort: Set to True to have the contents of the combo box automatically sorted alphabetically.
Combo Type: This sets the type of the combo box control. Available types are:
Drop-down: Provides a drop-down list of options that the user can select from. Does not allow the user to enter their own text.
Drop-down Edit: Provides a drop-down list of options, and also a text field that the user can type into. This lets the user choose from a predefined list or enter their own text.
Simple List: Provides a flat list of options (always displayed, rather than as a drop-down) and a text field that the user can type into.
Max Length: If the combo allows the user to type their own text, this lets you specify the maximum length of text that can be entered.