In Bartók’s 44 Duos for 2 violins Sz. 98 I found this caesura-like notation which appears not to exist in SMuFL or Bravura. Under “Holds and Pauses” the last entry, U+E4D7 caesuraSingleStroke has no glyph, and I suspect that would be a diagonal stroke anyway. It appears to fulfil roughly the same function as a comma, although there are also commas elsewhere in the collection.
There is an ornament sign which might serve, called ornamentVerticalLine: U+E583:
I recall, not sure from where, that Bartók uses this mark to tell the player to shorten the previous note slightly to mark a phrase-end, without adding any time. The comma is intended to add a little time, and so it appears in all staves.
Hope that helps
The comma in Dorico is staff-attached though, while the // caesura is system-wide. There’s no info in the edition about these notations, and I did also find one instance (in #40) where there is a comma on just one of the two staves. At least I can make U+E583 into a playing technique, thanks for the heads-up
I’ve found this symbol used in choral editions as well as an alternate breath mark. I believe I accomplished this by altering the default breath mark and then moving them into place. Might be a hack but it can be done.
The Single Stroke Caesura will be added to the SMUFL 1.4 Standard. All new symbols doesn’t have a glyph yet.