* Upgrading from LyX 2.2.x:
-The format of preference and session files has changed. LyX 2.3.x is able to
-read old files but will save them in the new format.
-
-The format of layout files has changed but, as before, layout2layout.py will
-convert older versions to the new format automatically.
-
The external_templates file has been split into one file per template,
which are now located in lib/xtemplates/*.xtemplate. This makes it easier
to add new templates or modify existing ones. If you have modified
the external_templates file, you will have to move the modifications to
the respective *.xtemplate file manually.
+By default, LyX 2.3 forces output of all en and em dashes as -- and ---
+when exporting to LaTeX. This can lead to incorrect line breaks, wrong
+characters in typewriter fonts, and problems with some LaTeX packages.
+Unselect "Document->Settings->Fonts->Output em- and en-dash as ligatures"
+to keep the LyX 2.2 behaviour and avoid these problems. See chapter 3.9.1.1
+"Dashes and line breaks" of the User Guide for details.
+
+ZWSP characters (u200b) following literal em- and en-dashes are deleted by
+lyx2lyx when converting to 2.3 format. If you used them as optional line
+breaks after dashes, convert them to space insets before opening your
+document with LyX 2.3 or the optional line breaks will be lost!
+
If using TeX fonts and en- and em-dashes are output as font ligatures,
when exporting documents containing en- and em-dashes to the format of
LyX 2.0 or earlier, the following line has to be manually added to the
2) provides explicit consent to the use of the converter on the first
compilation of the R-enhanced document.
+LyX now gives a warning if a document mixes title and non-title layouts.
+In some cases, this warning is harmless, but in other cases the document has
+a serious problem even though the LaTeX command does not exit with error. For
+example, create a document with a title layout, then a standard layout, and
+then an author layout, and you will see in the PDF that the author is not
+typeset as an author.
+
* Upgrading from LyX 2.1.x:
The format of preference and session files has changed. LyX 2.2.x is able to