How to set LastPass to verify before opening my vault and viewing all passwords

You need to edit your Lastpass preferences. In Firefox, if I click on the icon for the Lastpass extension and go to Preferences, I can check "Automatically Log out when all browsers are closed", and/or "Automatically Log out after idle (mins)". You can also enable the password reprompt as suggested by other answers.

It's up to you what level of security vs. convenience tradeoff you want to make. The default of staying logged in probably assumes you are on a private computer which will be locked by the OS when you're away from the computer, but that assumption obviously isn't safe in all circumstances.

The Lastpass options available differ quite remarkably between the browser extensions and the website.

To require the master password for every site password view:

• Login to your account on the website (https://lastpass.com)
• Click "Account Settings"
• Open the advanced settings (Button at the bottom of the popover)
• Look for the section "Warnings", then choose your liking among "Master Password Re-Entry"

I agree that this process unnecessarily convoluted and cumbersome.

Personally, I rarely ever need to actually see a password. I let Lastpass fill out the credentials for me and this works very well on most sites.

However, I suggest you use a second factor like TOTP (wit Google's Authenticator for example) for account login.