Click on the "settings" button next to the schedule you want to freeze. After that, click on "more settings". After, scroll down until you ses "Advanced settings". Click on it. Scroll down to the bottom again until you see "freeze schedule". Click on it.
Note: you can also freeze your account, which will in essence freeze all your schedules at once.
There's also a new functionality called "Holiday" which allows you to take a planned break on said day you have selected if that's what you're looking for.
