New in Mozart 15
Mozart 15 was released in November 2020.
It introduced the following new features.
Bar numbering
Bar numbers may be placed to the left of the bar or centred, and above or below the staff.
Fine-positioning of 'redirections'
Segno, Fine, DS, DC, Coda,... signs may now be positioned with more flexibility.
Alt + .
Fine-positioning of bar numbers
Bar numbers may now be positioned with more flexibility.
Alt + .
Font face for new files

Starting a new file by any of the three traditional methods now offers a choice of jazz or classic music fonts.
Laissez vibrer
The instruction 'laissez vibrer' (to let a percussion instrument
ring) is now available as text (l.v.) as it always was, but also now
as a 'tie to nowhere':
Multiple bars rest
Numbers on multiple bars rest now clear the staff lines.
Incomplete bars on a system
If a bar is so long that it will not fit on a complete system, the convention* is to end the system without a bar line but with a continuation symbol, now available in Mozart, as shown here.
Paper colour
The on-screen paper colour may now be set.
Text font styles
Font styles are now divided into two separate groups:
One set is designed for text boxes attached to the page: titles, header, footer, ... The other is for text in the music: expression markings, technical instructions, etc.
When you change the size of the printed music, text within the music always scales with the music, but you can now demand that the sizes of titles, composer-credit, etc. are unchanged.
Extracting Musician Parts
from a score
This process is now significantly refined.
Accordion register symbols
Accordion register (coupler) symbols are now available:
Editing hidden staves

Editing hidden staves is now facilitated.
When you expand the score to show staves
which are normally hidden, the image of the page expands
automatically to make room for them, with the expansion area being
shown in light grey as a reminder. On printing you will be invited to compress to score to hide all
staves which are marked as hidden. (This applies to all unwanted parts, including the virtual conductor.)
Extended copy and paste operations
Hitherto, the copy command has worked on a selected block of music, copying everything within the selected block.
The same Copy comand will now also work on certain single highlighted items (including text and dynamics). In this way a given piece of text (for example) can be pasted at various points in the music without redefining it in the text entry dialogue box.
Entering dynamics (etc) in multiple parallel parts
After a dynamic (f, mf, mp, p etc) has been entered, there are now commands to enter the same dynamic in some or all parallel parts, in a single command.
Copy to bracketed staves:


Copy to all strands:
?
Deleting dynamics/sforzandi,...
There are now more methods for deleting items of specific classes.
Notes in parentheses
Notes may be placed in parentheses to provide "ghosted notes" for jazz or long glissandi:
Continuity of parts on changing systems
Mozart now supports arrow indications at the end of systems where voices change from separate staves to a joint staff, and vice versa:
Hiding stems
Mozart now supports hidden stems (for specialist purposes).
Caesura (break) //
Mozart now supports play-back of a caesura (or 'break') - the symbol //.
The play-back duration may be chosen in much the same way as for a pause (fermata).
'Slash notes'
Mozart now supports 'slash notes' in two alternative styles:
Combining these styles with the 'hidden stems' option (see above) allows stemless slashes, for example with attached chord symbols as used to define a jazz solo in a big band part:
Exporting abc files
Export of abc files is improved, with abc's '>' notation used for dotted notes.
Modes
It is now possible to assign a mode to a piece.
This is carried over when importing and exporting abc files.
Extracting parts from a score
All parts may now be extracted from a score with a single command. Names are generated automatically.
↓
Imposing a layout
You
can now select a layout from a collection of .mzlayout files, and impose the layout on the current document.
This facilitates giving a uniform appearance to a number of files.
Automatic beaming
The automatic beaming of notes as you enter them has been improved to be more in line with standard practice.* For example:
List of text boxes
The dialogue listing text boxes now has a quick way of deleting a text box.
Access to help
The various commands listed under help are now presented on their own category tab for more convenient access.
Mouse Wheel
Ctrl + MouseWheel now zooms in and out. The MouseWheel without Ctrl scrolls music vertically as before.
(This brings Mozart into conformance with the behaviour other programs including Microsoft Office.)
A new tablature command
There is now a command to move a note to a different string preserving its pitch:
This facilitates adjusting tablature after copying and pasting from a stave with normal notes.
Entering tuplets
A new, quicker way of entering tuplets is available.
The standard commands work as before, splitting a note into a tuplet
when the caret is on a note, but now they also enter a tuplet when
the command is issued with the caret 'in space'.
Bracketed passages
As well as the standard options of solid, dotted, or dashed lines, bracketed passages now have the option of a vertical terminator or none on the end.
8va passages have the option of being marked 8va or 8 - and similarly 8vb or 8, etc.
Pulling bar brackets
1st/2nd time bar brackets can now be moved up and down with 'Pull' commands (Alt+↑↓) as well as with the bar-line properties dialogue box.
High DPI (including "4K") screens
Mozart is now optimised for use both on standard screens and those with high resolution including "4K" screens (which have of order 4000 pixels across). In particular, irrespective of resolution:
- New music is presented on the screen at an appropriate size;
- images on the ribbon bar and on dialogue buttons scale appropriately;
- images in the help system and tutorial scale appropriately.
...
*Reference

In 2011 Faber Music published "Behind Bars" (subtitled "The Definitive Guide To Music Notation") by Elaine Gould.
As noted earlier we continue to take this work as the gold standard for recommended good practice.