Chrome for iOS beta allows you to lock your Incognito tabs with Face ID or Touch ID
The update will be available for iPhone and iPad and is currently a part of the Chrome app’s beta version. What it does is actually blur Incognito tabs in the tab switcher until you authenticate with fingerprint or facial recognition. Enabling this feature will help you protect the Incognito tabs from other people when they are borrowing your iPhone for a quick Google search, for example.
The feature is not available to all beta users yet, and it’s unclear when the update will become available to all. Once you have it, you can turn it on via Settings > Privacy > and then enabling “Lock Incognito tabs when you close Chrome”.