Is there a reason you want to do this? Tempo changes should normally be done with tempo texts, not via the play panel. That's just for temporary overrides - like for practice purposes to hear a score slower than the actual marked tempo. And since the tempo may change over the course of a piece it isn't really clear what a tempo typed into that dialog would even mean. That's why instead, it's specified as a percentage, which you can indeed set directly.
Comments
Is there a reason you want to do this? Tempo changes should normally be done with tempo texts, not via the play panel. That's just for temporary overrides - like for practice purposes to hear a score slower than the actual marked tempo. And since the tempo may change over the course of a piece it isn't really clear what a tempo typed into that dialog would even mean. That's why instead, it's specified as a percentage, which you can indeed set directly.
I close this issue since it's apparently a misunderstanding. Reopen if necessary. See my remarks about feature request ending with ? http://musescore.org/en/node/24750#comment-95807