For the times when you don't want to speak to your phone and tell the whole world you're turning on your bathtub or locking your front door, Google Assistant offers a keyboard input method which lets you type your requests instead. Suggestions used to show up when using this input, but then they disappeared either entirely or for many people. Now, they seem to be back for lots of users.
Simply trigger Assistant and tap the keyboard button at the bottom. You should see a list of suggestions. In my case (leftmost screenshot below), these are my most used commands taken from my Assistant history. In Ryne's case (screenshot at the top of the post), these show up below the text input field and seem more contextual.
The suggestions improve when you start typing, with autocomplete options taken from your history of Assistant requests as well as some popular suggestions. However, they don't seem to be integrated with your Google Home devices, so if you've named a smart light "Green Lantern" and you start typing "turn on gre..." you won't get that suggestion unless you've used the command before and it's saved in your history.
Left: Suggestions before you type anything. Middle & Right: History and autocomplete suggestions.
These suggestions are live for our tipster with v10.97.6 beta of the Google app, and also for several of us here at Android Police with the latest stable v10.97.8. They may be triggered server-side, but it doesn't hurt to grab the most recent Google app version from the Play Store or APK Mirror to increase your chances of getting them.