Game and Plater version
Plater-v564.2-Retail - DFv468 - 10.1.7

Describe the bug
Buff special "Show Timer" toggle doesn't work, timer is always shown.

Works perfectly fine on my end.
I suggest trying with only Plater enabled and a default profile.
This might be due to some mod from the modding tab or OmniCC or similar addons.

You're right, It works fine with default profile, but not with modified with omnicc enabled. So problem is just somewhere there, I believe. Auras (buffs/debuffs) works just fine (timers through omnicc, not plater), but not ExtraIconRow.

And on that second one the timer is disabled in the options?
No mods on the modding tab that change anything for timers?

Any screenshot?
Usually that setting won't apply for OmniCC timers, just for the plater default one.

Default profile

Modified

Thank you, found one. It was "Buff Special Mod".