I'm stumped: what is "playback designer"?

Playback designer can be found in the expression dialogue and is used to "tweak tempo changes"
I have learned that this does not work for version 25 – yet, regrettably.

James,

Thank you for the explanation. I would recognize that as the Playback tab of the Expression Designer. (I understand from your other post that you are new to the program.)

Ritards are usually handled by Human Playback (HP) rather than by settings in the Expression Designer, even though originally ritards and other progressive changes relied on playback shapes set in the expressions menu.

I will simply say that I have always found calibrating the rate or slowing in a ritard to be a challenge. I wish a future version of Finale would allow one to set an initial tempo, a final tempo (pinned to a measure location), and a rate of slowing (straight-line or parabolic), but so far that has not appeared.

Make sure you have set an  HP style in the MIDI/Audio menu. It is probably already set to STandard, but it doen't hurt to check.