In some SAP lists you can navigate through SAP by clicking on a line in a list (For example, run FB03 for a document, then click environment->accounting documents and you navigate this way). How is this accomplished in GuiXT?

You can implement this with the commands

SetCursor (x,y)
Enter "/2"

in an InputScript, where (x,y) are the cursor coordinates on which you want to click. For example

SetCursor (1,8)

would select line 8. It is also possible to scroll thought the list automatically if necessary.