How to use both Flutter stable and dev SDK on the same machine?

I found this Dart package called Flutter Version Management that does exactly what I want.

As the docs says:

Flutter Version Management: A simple cli to manage Flutter SDK versions.

Features:

• Configure and use Flutter SDK version per project
• Ability to install and cache multiple Flutter SDK Versions
• Fast switch between Flutter channels & versions
• Dynamic SDK paths for IDE debugging support.
• Version FVM config with a project for consistency across teams and CI environments.
• Set global Flutter version across projects

https://github.com/leoafarias/fvm

Now I just need to add FVM_HOME/default/bin to the PATH and FVM will take care of everything...

You'll need to setup alias to switch between different environments easily.

See here a detailed article for that.