UX improvement - Flow - Collapse & Expand

There's two parts to this:

1. Ability to collapse and expand individual containers.

2. Nice to have:

   1. Ability to collapse and expand everything in one go; e.g. adding 2 new options / icons in the panel with the zoom and 'full screen mode' links.

   2. Ability to remember if containers were collapsed / expanded upon last save so that when flow is reopened it is in the same state I left it / saved it in.

This would be useful for large flows and people (like me) editing flow on a small laptop screen.

I see this working similar to code editors, where you can collapse and expand chunks of code.