Ability to set local password

If you use a standalone vault just for a shorter password, you're using 1Password not as intended. There are many functions that make you entering the master password less often.
Windows desktop app: use Windows Hello, that means configure Windows to accept a PIN in addition to your Windows password. Then configure the 1Password desktop app to unlock with Windows Hello, which means it accepts the Windows PIN in addition to the master password.
Browser plugin: Use the current browser extension, not the classic extension, and configure it to integrate with the desktop app. This way the (Window Hello) unlock is shared between desktop app and browser.
Android: Configure fingerprint unlock, or if unavailable, unlocking via PIN.

In all these cases, you need to enter the master password only once after you reboot the device and not again while the device is still running.

And don't hesitate to change your master password to something easier to enter. A login that isn't used, just because the password is too difficult to enter, isn't a good login. If your common passwords are in your local vault behind an easy local password, these are not very secure. These are at risk. Find a good middle ground. I, for example, switched to a master password that doesn't contain any characters that require some modifier key such as SHIFT to enter except with letters. But since this is easy to type even on a smartphone, the password is rather long.

Is local vaults not going to be supported in 1Pass 8 or has it just not been implemented yet ?

I use a local vault since I do not want certain logins syncing back to the cloud. If 1Pass 8 will not support local vaults - will there be a utility to get those login's exported out ?