Ability to set a (vibrate watch only) alarm for lucid dreaming

I’ve just got this app to aid with lucid dreaming. I found settings that make the lucid dreaming option to vibrate my watch only (no sound from phone). It’s my understanding that there’s no way for me to test this yet other than waiting for when I sleep tonight when the app thinks I’m in REM and will be triggered.

However, I noticed that when creating a manual alarm there is no option for vibrate only, if you set it to silent it does not vibrate. It only shows the screen.

It would be great to have a kind of WBTB alarm which wakes me up with my own pre-set time. This would be especially great for me as I don’t like waking up my partner with noisy alarms in the middle of the night.