External References in Sketch HCM
In the Sketch HCM it is taken into account for HCM constraints whether the use of external references has been activated or deactivated. An external reference exists if a HCM constraint refers to a part that does not belong to this sketch.
For existing sketches, the use of external references is activated by default to keep the existing behaviour of these sketches. Newly created sketches follow the setting in the Configuration Editor at System settings > Sketch HCM > Use external references. New installations will use external references by default.
If you right-click on the empty area of the HCM window of the ICN, a context menu with the options External reference: Use or ... do not use, respectively, will be displayed, which shows you the current setting for external references. Alternatively, you can use the 
button that is part of the toolbar in the HCM area of the ICN to quickly enable or disable the use of external references in the Sketch HCM.
HCM constraints with external references are marked with the 
icon in the ICN.
Activated external references: If the part to which an external reference refers is moved or changed in some other way, the HCM model will be adjusted to it. If this updating does not take place automatically, it can be carried out manually by choosing Sketch > HCM > Update system. If the part is deleted, the HCM constraint will be invalidated and deactivated.
Deactivated external references: The part to which the external reference refers has no influence on it. Even a manual updating of the HCM model will have no effect. However, the link between the HCM constraint and the part will be preserved, meaning that the external reference may be reactivated with the corresponding function.
The use of external references can also be activated and deactivated in the HCM window of the ICN.
