You've got good advice from Susan.

If you'd like to indicate "COVID-19" or whatever other texts on top of the return, click on General > Misc. Info./Direct Deposit on the left navigation panel, scroll down to the bottom of the input screen for the line Form 1040 text, and type in any text of your own choosing.  Like we discussed in various other threads, nevertheless, it is unlikely the IRS will pay any attention to these texts and including it will unlikely offer your client any protection since there is no statutory, regulatory, or instructional requirement for doing so.