Currently, merged PRs doesn't show if the checkbox "Delete <branchname> after the pull request is merged" is enabled or not. We'll have to use the https://developer.atlassian.com/cloud/bitbucket/rest/api-group-pullrequests/#api-repositories-workspace-repo-slug-pullrequests-get to verify this. It would be good to have this added in the PR view so users can easily know if a source branch of the PR was deleted on merged.