Can I manually amend an imported W-2? I made excess contributions to my 401(k) due to multiple employers in 2018 and should be getting a 1099R next year.

Going through reporting additional income under misc. income in turbotax requires submitting form SS-8, which I don't believe is applicable as I already have a W-2. Pub 525 (for 2018 taxes) also says the excess contribution should be included as part of regular income in box 1 of my 1040, which I believe includes a strict sum of box 1 W-2s.