As a Scrum Master I want a way to zoom in an out of the roadmap so that I can easily see the roadmap for the time range that I want.

The current +- zoom doesnt give me full control over how much zoom it add or subtracts. For example if I am tring to see a 5 year roadmap and the I start zooming out from 4 years, it zooms out to show me 6 years. I don't want to see 6 years, I only want 5 years. If I zoom back in again it goes back down to 4 years.