That function is directly available in Lacerte. https://proconnect.intuit.com/community/permissions/help/lacerte-software-developer-s-kit/00/102313 would might offer some help if you are really into learning some new skills.

If you are moving from another software, I would import into 2019. Do a bit of massaging to see if  you have the correct numbers to proforma, go to Screen 3 and remove the check box in the first section for Converted Client. Then do the proforma to 2020. That will mean you are really ready to go when you need to file the returns.