Create dim variabel to control dim time?

I don’t have Pro so I don’t get access to eventual apps that can be used for this purpose.

I have a z push button I have set to dim wiz bulbs, controlled via a flow. It dims, it’s just that it dims so fast it’s impossible to stop at a certain level. So in pracise it’s either 100 or 1%.
I want to create a variabel that can control this time, in steps that’s, if possible seamless. I am so so bad at creating variables. Maybe becaue I don’t understand how they work, what they can do and how it’s created.