We've not yet moved a DocLink customer to v2018, yet it seems that they need to confirm that the screen customizations are still correct, fields are in remain in the right place, and don't run into any other customizations the customer may have on that screen. We do this as part of our upgrades, too, eventhough there may not be any action needed. If they have an importable file for their screen customizations, they could remove/overwrite any others that the customer has, which would be worse.