Mercurial isn't yet supported in the Windows version, however will be added very soon. The FAQ states "Due to time constraints, only Git is supported in the beta version. Mercurial support will be coming later in version 1.0."
Hope that helps
Supported Platforms macOS Windows To make using Sourcetree as simple yet powerful as possible we embed (bundle) dependencies such as Git, Git LFS, and Mercurial. We strive to keep these...
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