At the moment, the feature is currently not available in the platform but thanks for sharing your feedback. You can send feedback to the team by scrolling down on your home page and clicking 'Feedback' in the left bottom corner. While the team can't respond every comment, please know that we read and appreciate every suggestion that comes our way.
Unfortunately, that's not possible. However, you can update your password in Settings if you want your account to be inaccessible from another device until you enter the new password.