Adding text to textbox from a list

Question

In our application there is a form to specify command line arguments to run an EXE with. We also want to provide some keywords that the user can use, now we put them in a listview. Currently, it looked like this:

When the user double click on an item in the listview, it will be added to the current caret position in the textbox. The text can really span a few lines, that's why the text box is quite big.

Is there a better way to have this functionality? The problem with current design:

• It looks weird because the listbox is not as wide as the textbox
• It takes a lot of vertical space (listbox + textbox)
• The two controls are quite separated vertically, due to the height of the textbox.

How can this be improved?

Answer 1

The best way is to use autocompletion. Autocompletion is good because user will be able to insert parameter value instantly (i.e. without leaving text area and switching to other controls, etc):

Other possible option I see is to use Insert macro button with variants:

And if there are just a few of items, you may try to place separate button for every macro above or underneath the text area. It may also be used in parallel with the autocompletion: