One of the best ideas is that due to security issues, it is better to use pass lock in Firefox, in which case it will be used in a personalized purpose.
@SergThank you, Its like screen lock in phone for access the phone if you want to enter the personal browser you must enter password, I attach my idea like image below, you can check it
I see, it looks like an extension to Primary Password. Just want to note that while it adds a bit of protection, it can not stop a half serious attacker. Locking device with OS provided mechanism would always be more secure.