Notion's rhythm notation is a useful feature, particularly for rhythm guitar and piano accompaniment when you want playback of chords. But that isn't what was being asked.
Slash notation is, as Wikipedia put it, "purposefully vague" about the rhythm, and requires stemless slashes placed on each beat. If you use four quarter notes in Notion and convert to rhythm notation, they will have stems. If you look at the example in my earlier email, the slash marks in this case are stemless, even though there are four per measure. They are intended to indicate situations where an accompanist can improvise an appropriate rhythm. Or it may be used to keep time during a solo passage where the rhythm is not specified. This would specifically NOT be included in playback, even with chord notation. It would be a notation feature only.
I've attached how it looks in MuseScore (ignore the silly music, this is just a test example):
- MuseScore slash notation.jpg (29.55 KiB) Viewed 23592 times
And an example of why Notion can't handle it using rhythm notation as currently implemented:
- Notion rhythm notation.jpg (8.04 KiB) Viewed 23592 times
Whole notes don't look like slash notation and mess up the meter if you put four in one measure. Quarter notes in Notion's rhythm notation have stems, which implies a quarter note rhythm instead of an improvised rhythm. MuseScore has the ability to notate this correctly: four quarter note slashes with the stems removed.
I'm not sure how anyone can print out and use a jazz score for real players using Notion without it, other than maybe printing blank measures and writing the slashes in by hand. I don't use it for printing purposes, so it doesn't affect me, but I can see how the lack of this feature would be frustrating.
There are a few ways this could be implemented from a user interface standpoint. There could be an option to remove the stems from quarter notes, which would allow them to appear correctly when converted to rhythm notation, but the program would have to know not to play back quarter notes without stems. Or they could be a new symbol on the note palette, implemented as an alternative type of quarter note rest (which would have the benefit of not being played back).