combo boxes, list boxes and push buttons are default basic components and well documented on sites like wikipedia.
The form field name will be editable after the next update, do you need to be able to change the type?
There seems to be a bug with copying and pasting form elements, as cutting with ctrl+x works but pasting doesn't, I have created a ticket for this issue. A multi-line field means the user can enter multiple lines into it.
The Mouse events are Widget events defined by their name, e.g "mouse enter" will perform a certain action like open a webpage if the user viewing the document moves his cursor into the area of the widget.