When you open the dialog box to reply... the tag line space is directly underneath. Try it. Attempt to reply to me. You’ll see the spot. Click on the single line box with your cursor and enter your tag line.
LOL I had one up until a couple days ago—just accidentally erased it...the good idea was for the person to whom I was replying that they should use their sentence :)
But, I should redo mine, and I will...tomorrow when I am not so tired ;)
BTW, with my last tagline, I had started listing Trump endorsements, but I ran out of room :)
Thanks for suggestion, and I hope others see how to do it :)