Yes - go to the Hotkeys tab in Settings and make sure a hotkey is set for 'Save Clip'. Then go to the Options tab, the 'Clips' section and set that to 30 seconds or whatever you need.
Then when you're recording (you need to be already recording), you can hit the hotkey and the last 30 seconds of gameplay will be saved to an MP4 file. You'll see it saved in your 'Recordings' tab.