I'm preparing 2020 return. I'm entering my home office deductions for 2020 but the empty boxes say 2018 and 2019 instead of 2019 and 2020.

The form 8995 for Home Office Deduction is currently unavailable for 2020.  It is scheduled to be released by the IRS on February 4, 2021.  You may complete that section of the return at that time.  

Home offices became primary workspaces for many people this year. Most W-2 employees won’t be able to deduct home office expenses on their federal return, even if they’ve been asked to work from home due to COVID-19. But, some states do allow W-2 employees to deduct these types of expenses on their state returns. We’ll check for every possible deduction and any state-specific tax breaks to get you your best tax outcome.  Here is a link to additional information to determine if you can take the home office deduction.

Can I take the home office deduction?

As a side note, IRS will not start processing returns until February 12, so there is still plenty of time to get it done.