If you do not need to modify the time and reminder modes, then you can add reminders by using only the keyboard:
1. Type the desired reminder message in the message field then press TAB to advance to the next field.
2. Type the hours then press RETURN then press TAB to advance to the next field.
3. Type the minutes then press RETURN then press TAB to advance to the next field.
4. Type the seconds then press RETURN then press TAB to advance to the Add button.
5. Press RETURN to add the reminder to the list.
P.S. If you made a mistake you can press SHIFT-TAB to go back to a previous field.