[sameenkarim]

When you're using the UI to open a PR, if you set the base to a branch that has an open PR there'll be an "Add to Stack" option: https://github.github.com/gh-stack/guides/ui/#step-2-create-...

Stacks require users to explicitly indicate that they are opening a PR that should be part of a stack.

[herpdyderp]

It's very confusing that the "quick start" guide says the CLI is a requirement, when it's apparently not. This UI flow is exactly what I want! Thank you!