You can input tempo marks using the tempo popover, both during note input and by adding them to existing music.
Procedure
Result
During note input, tempo marks are input at the caret position. Gradual tempo changes, such as rallentando, are also input at the caret position with a default duration of a quarter note. Gradual tempo changes do not extend as you input notes.
When adding tempo marks to existing music, they are added at the rhythmic position of the earliest selected item. Gradual tempo changes span the duration of the selected items.
Metronome mark values appear as integers without decimal places by default, even if you input decimal places. However, the exact metronome mark value you input is always reflected in playback.
After Completing This Task
You can lengthen/shorten gradual tempo changes.