Prerequisites
The car frame is finished and saved with its CAD models in place.
Steps
1.) Position a CAD model using DigiPara Liftdesigner 3D parameters and/or fixed values. Select the CAD model and, in its Properties window, set its position using a combination of a fixed value and a DigiPara Liftdesigner 3D parameter — for example, where a model's base point isn't located directly on the geometry but the design already accounts for a specific cabin width, combine that fixed offset with the current car width parameter. This links the CAD model's position directly to the current car width.
2.) Mirror the formula for the opposite CAD model. Copy the position formula from step 1 into the corresponding Properties window field for the model on the opposite side, using the copy function, then manually adjust the signs so the mirrored model ends up in the correct position.
Result
The car frame's CAD models are now positioned dynamically, following the car width instead of a fixed value.