In BikeCAD version 11.7, we have the option to model down tube or bar end shifters. You'll find this option in the drivetrain dialog box under the shifters tab. Most road bikes these days have shifters integrated with the brake levers. This scenario is already illustrated here. For integrated shifters we would leave this menu set to Other/None. Even with this type of setup, we may still choose to add a down tube shift boss. We can do this with the checkbox provided. The shift boss will be located the specified distance from the end of the down tube. If we enable the eyeball icon, BikeCAD will display a down tube cable stop over the shift boss.
If we do want to use non-integrated brake levers, we may then choose to use down tube shifters which are available from the menu. The angles A1 and A2 are used to indicate the two extremes in the range of motion of the shifters. We can see that as we run through different cogs from low to high gear our rear derailleur shifter will adjust to reflect the chosen gear.
Bar end shifters are also an option. As with integrated shifters, we have the option to include or not include a down tube shift boss. When using bar end shifters, we can choose to mount them at the end of our drop bars which is a popular choice for touring. We can also mount them to the end of bullhorn bars. However, if we are mounting brakes to our bullhorn bars, we will probably want to select the Aerobars checkbox to relocate our shifters to the aerobars. We will not actually see the aerobars or shifters until we turn on the display of the aerobars in the aerobars dialog box.