Short version:
Microsoft Lists: new Integrate drop-down menu: As part of updating the command bar at the top of Lists, Microsoft are introducing a new top-level menu item: Integrate. This is the home for features that help extend list experiences. Due by mid-April for most of us.

Details:
As part of updating the command bar at the top of Lists, Microsoft are introducing a new top-level menu item: Integrate. This is the home for features that help extend list experiences. 

The existing command buttons for Power Apps and Power Automate: 

Once the new experience is available, the Power Apps menu option will disappear. You will need to navigate to the Integrate menu option to access both Power Apps and Power Automate.


Availability:
This feature rollout will begin late March for targeted Organisations and should be complete by mid-April for the rest of us.

Links:

Microsoft 365 Roadmap ID 64869