X-mas lights random turn off between times, using UI, no Yaml editing

Hi All

I have created an automation using the UI where the light turn on at sunset and turns off at 2300, but I want them to turn off at a random time around 2300, say between 2245 and 2330. I was surprised when I found no easy way to do anything like that in the UI? It must be me the NOOB not knowing where to look or who dont quite understand how it all works. I was searching for hours for a solution, but only found tricky stuff about changing the Yaml file, which I want to avoid if at all possible.

Can someone tell me how to do just that?