Choose the modifier key you want to use in PitStop Pro.
You have the choice between CTRL (on Windows) and CMD (on Mac) on one hand, and SHIFT on the other hand. It's not possible to use the same modifier key for both functions.
This is workaround for users working with the Adobe Output Preview dialog, which does not support the PitStop Edit tools in combination with the SHIFT key. Hence, to make use of the functionality to select multiple objects and constrain the Edit and Select tools, you should set this preference to CTRL/CMD (instead of SHIFT).
For more details, refer to PitStop Edit Tools: modifier keys.