I want to enter a longterm capital loss carryover in Schedule D, but I did not use that loss in 2018. Can I enter the Sched D info from 2017 instead?

If you are certain you have not used the capital loss carryover prior to 2019, you can manually enter the capital loss carryover.

Click the "magnifying glass Search" icon on the top row, enter "capital loss carryover" in the search window and press return or enter, and then click on the "Jump to capital loss carryover" link to begin entry of the capital loss carryover.