In iOS 12 clock app, you can control whether each alarm vibrates. In the timer section, you cannot control whether the timer vibrates.
This question has already been asked here: How to disable vibration for Timer alerts?
However, iOS has changed so that the workaround of disabling vibrations on alarms no longer disables vibrations on timers... due to the fact that you can no longer disable vibration on all alarms but control each alarm individually.
I do not want to disable all vibrations with the mute button. Is there a way to control specifically how the timer behaves?