You have two options to select multiple items from such lists. These options work on Windows and Macintosh and are not specific to ConfTool but work in many applications.
Hold the CTRL key and click the items in a list to choose them. Click all the items you want to select. They don’t have to be next to each other.
Click any item again to deselect it, e.g. if you have made a mistake. Remember to keep the CTRL key pressed.
If you want to
select items that are adjacent, you can use the
SHIFT key. Click the first item, then press the SHIFT key and hold it. Click the last item and release the SHIFT key. To select adjacent items, you can also use the mouse. Click the left mouse button on the first item, hold the mouse button, move the cursor to the last item and then release the mouse button.
You can also use both SHIFT and CTRL keys together. For example: You can deselect an item from a row selection that you have created with the SHIFT key when you hold the CTRL key and click the item you want to deselect (see image).
Simply try out both options and play around until you have familiarized yourself with them.
NB: The CTRL key has the label STRG on German keyboards.
Please see a related
Wikipedia article.