He Mark,
I know that chord symbols are a far from perfect tool.
And I know, as mentioned earlier that #9 is dominant in use.
But I come across the use of b10 reasonably frequently and also use it myself quite often due to reasons mentioned in a previous message to Fred.
So an easy input of b10 just as with #9 would be nice.
Especially because (via shift Q) you can input #5 and b13 in the same symbol as you can #11 and b5. LOL
That’s in fact all I ask for.
Please forgive the question,
But why then call it a C7 (#9-b9/ b13) and not a C7 (b10 - b9/b13) ?? Just out of habbit or convention???
I would never do that. 
You could also just call the chord C7alt, which means (for some) that the chord has Root: C, Major third E, low seventh Bb, a real dominant-chord. Alt means that the Fifth can be b5 or/and #5 and the ninth could be b9 or/and #9. Choose your chord-notation as you wish, and notate in the score what looks most logical. In our example it looks most readable with only flats.
And so the show (discussion) can go on. It is religion in the eyes of non-believers.
C7#5 indicates a strong and simple dominant with an up-leading 5. In C7(#9b13) the altered notes are leading downwards. Notated with an b10 on top. Confused? Fine. But that’s what I prefer.
In advanced chords there is a rule: the interval b9 may only appear up from the root. I have often experienced that if a chord sounded “wrong” the reason could be another b9-interval.
And nevertheless the chord from bottom up: C-G-E-Bb-Eb-Ab-Db-Gb sounds good. The reason is that in the “bottom” unaltered intervals sound best. And all the black notes here are naturals sounding up from the low C. But That’s another story.
Daniel, Fred, Dich and Mark,
I’ve really enjoyed exchanging opinions.
As some of you have pointed out, the sounding music is eventually the thing that is most important.
I think that composers/arrangers should facilitate this music in the way they see most fit and music notation software should facilitate them to do this in the most convenient way.
I think enough is said, so back to doing the important thing, make some music!
Best Wishes to you all,
Harald
PS
@Dich: like the chord! 
Is that really a rule if no one follows it? 
Duke Ellington, Blue Serge,, Gb over F
Charlie Barnet (arr. by Billy Moore Jr), Skyliner, Db over C
Thelonious Monk, Little Rootie Tootie, Gb over F in this Eb demented chord, LOL
Monk, Crepuscule With Nellie, D over C# (Db?)
Brookmeyer, lots including ABC Blues, Willow Weep For Me, St. Louis Blues
Wynton Marsalis, “Sweet Release, Home: Beyond This Rage” Cb over Bb, G over F#
I’m sort of joking with this as you clearly gave the example of the Ab over G interval of a minor 9th in that C7alt chord, but it is an interval that has to be handled with care. Ellington actually uses this a lot, but I’ve realized he almost always has at least a 4th between the top note of the voicing (causing the minor 9th) and the next note, so the added separation makes the melodic note stick out in spite of the dissonance. There are a bunch of examples in Tone Parallel to Harlem too.
Impressive Fred, Nice examples.
About rules.
Just one (well in fact a coupe) things about them.
One thing is that in playing practice lots of theoretically strange things can happen because they lie “under the fingers” and turned out to sound cool. See example
As I think Miles Davis said once: “There is no wrong note until you hear the next one”. Meaning, I think, that everything should be judged within a context.
Sometimes a plane Dominant seven chord can sound very wrong although there is nothing theoretically wrong with that chord.
Also I think most Jazz educated musicians focus almost only on vertical chord structures and the scales they can play over them. The linear element is mostly neglected.
But just opening any work of J.S. Bach (e.g. the Goldberg Variation) and you’ll be freaked out of what is at all possible. Of course this isn’t one on one translatable to a jazz context but it can inspire and free up your mind from a rigid vertical way of thinking.
One nice (but also a bit geeky) youtube channel is Early Music Sources and when talking about theoretical rules the episode about False relationships is really interesting to watch.
Best,
Harald
Inside the Score pag. 119? 
Yep, great book!
I love the Monk examples. I also know the “Inside the Score” and learned from it. Gave it to a young student long ago. Thank you for the examples. And especially the “False Relations”
The b9-interval story here reminds me of J.S.Bachs hard work in his chorals for not making parallel Fifth’s - letting voices cross each other. But let’s not start another thread.
Last remark. Many years ago a dared to propose - in my class of jazz-students -that the melody in the C7(b10-b13) example, that the melody played b10-b9. The jazz-police reacted immediately.
And it would be a good thing if Dorico also was able to write b10-chords.
So I kind of forgot to comment on this topic, so my reply is a bit late. But in Dorico 4 the b10 input via the pop over is possible!!! Thanks so much Daniel and the rest of the Dorico team. This helps me so much… 
Keep up the good work.
Harald
Dorico rules!!! 
BTW, The jump bar also is great!!!
