Maintainers can't. Only the PR owner can.

For that to work the PR owner has to know which branch to target (assuming it's public).

Unless the PR creator somehow knows which release their PR is going to be included in, with a guarantee it'll be merged in said release, then it's just not possible for the PR creator to target the correct branch.

It’s a bit undiscoverable, but if you click the edit title button it will actually allow you to edit the base branch as well. Sibiling comment said this might be opt-out-able, but at least in ms/vscode no one seems to opt-out.

> Maintainers can't. Only the PR owner can.

Just tried it, seems to work fine for me..?

When filing a PR there's a "allow maintainers to edit the PR" checkbox (I don't recall the exact wording). If the PR owner doesn't check it, the maintainer can't change the target branch.