If you change the clef, Notion for iOS is going to move the notes to preserve the pitches. Normally this is what you would want, but in your unique case, I see the issue. The only thing that you can do in Notion is to use the select tool to highlight your notation. You can then go to "More" from the select tool menu and select "Transpose" under the "Tools" heading. You can then transpose by the desired scale degree.