Below you will find an extensive list of the work that went into MorphOS 3.13.
Please note that this is just an overview and does not mention or explain every new feature.
 
MorphOS 3.13 boot.img Changes

The following is a (probably incomplete) list of changes made between the 3.12 and 3.13 release of MorphOS to the ROM (boot.img) based components.

Quark

  • Fixed issues with Pegasos II shutdown
  • Fixed several issues related to the Pegasos I OpenFirmware support
  • Improved Sam460 support in 'SATA' mode
  • Silenced some debug output
  • Added FD=FWDebug boot argument for Pegasos I/II systems as well
  • Fixed issues with proper identification of PCIE PowerMac hardware and its registration support

Cybergraphics

  • Stability improvements

DOS

  • Improved RunCommand() state preservation and restoration
  • Refuse to boot an ISO that has newer MorphOS version on it
  • Fixed the boot code possibly picking a non-bootable device in some rare situations
  • Fixed a potential crash in CreateNewProc() error code path

Exec

  • Improved ColdReboot/ShutdownA handling
  • Fixed floating point rounding mode preservation

FatFS

  • Fixed a zero-page hit in ACTION_REMOVE_NOTIFY

FFS2

  • Fixed bugs related to default filesystem usage

Graphics

  • Fixed a use after free bug
  • Fixed potential race condition bugs

Intuition

  • Authentication screen's window cannot be accidentally iconified anymore
  • Fixed authentication screen resource leak

Log

  • Improved to show segment information for 68K exception program counter address
  • Improved FPSCR register display

PFS3

  • Fixed softlink support when link points to ":name"
  • Fixed a harmless off by one bug in softlink support

Powerbook

  • Fixed num lock led controls on some keyboard models

Ramlib

  • Fixed a bogus library version for the OldOpenLibrary call when debug was enabled
MorphOS 3.13 Disk Changes

Following is a (probably incomplete) list of changes made to the disk based components of MorphOS.

Ambient

  • Disabled wallpaper transitions on hardware with too little video RAM
  • Reduced overall video RAM usage
  • Fixed a race condition resulting in a crash when modifying icons

Applications/FlowStudio

  • Added gcc9 and g++9 compiler defaults
  • Fixed text measurement problems on startup when TTE rendering is enabled
  • Fixed jumping to functions with prototypes longer than ~90 chars
  • Tasks that were completed with single stepping could not be restarted in the debugger
  • Make sure that at least the 'MUI skin' option is always available, for instance if the Skins directory couldn't be found
  • Sets the correct PROGDIR for the debugged process

Applications/Odyssey

  • Updated the root certificates bundle
  • Updated to more recent cURL library
  • Fixed user style sheet load issue
  • Other minor fixes and improvements

Applications/Jukebox

  • Character encoding fixes

Applications/RDesktop

  • Fixed AHI audio related issues

Applications/Showcase

  • Fixed some busy looping bug in image browser thumbnail scanner if delayed scan wasn't enabled

Applications/Transfer

  • Stability improvements
  • Added missing UTC time conversion for FTP download

Applications/VPDF

  • Updated poppler library to 0.85.0
  • Fixed a Freetype related memory leak on close

C/Iprefs

  • Improved detection and reporting of booting the system with a wrong boot.img

C/PowerMac7FanControl New

  • Tool for controlling the fan speed and reporting fan status and system sensor temperatures on PowerMac7 systems.

Classes/Blankers/PicView.btd

  • Worked around the issue of screen going blank after a while

Classes/Frameworks/mui.framework

  • Fixed MUIString overloaders using String.mui instead of StringU.mui

Classes/Frameworks/ob.framework

  • OBArexx now works with old rexxsyslib.library versions

Classes/Mui/Scintilla

  • Fixed a zeropage read hit
  • Implemented support for subpixel TTE font rendering

Classes/Reggae/gif.demuxer

  • Added missing MMA_MediaType handling

Classes/Reggae/netpbm.demuxer

  • Added missing MMA_MediaType handling

Devs/Monitors/Radeon

  • Filter out resolutions that are provided by the connected monitor but can not be displayed by the connected graphics card output
  • Refuse to generate DualLink DVI output resolutions on R100/R200 family GPUs
  • Fixed iMac iSight dual head support

Devs/Monitors/SM502

  • Fixed displaying 16-bit modes

L/Apipe

  • Support for querying the amount of pending data in the pipe

L/SmbFS

  • Fixed a possible hit once the (optional) user/password window was closed on mount

L/Ssh2fs

  • Statibility improvements

Libs/Cairo

  • Fixed a possible memory leak related to unfreed Freetype/Font resources

Libs/Cryptostorage

  • Added new functions: CryptoStorageClear(), CryptoStorageExport() and CryptoStorageImport()
  • Improved debug output

Libs/Diskfont

  • Disabled some unused code

Libs/Freetype

  • Added support for configurable hinting mode
  • Fixed anti-aliasing issues with new freetype.library
  • Improved harfbuzz.library integration

Libs/Harfbuzz

  • Fixed several potential lock-up issues

Libs/Ixemul

  • Fixed lseek64 function return value for seek positions >2GB
  • Added pread/pread64/pwrite/pwrite64 functions
  • Optimized lseek/lseek64 function

Libs/PNG

  • Only open locale.library on demand

Libs/PPC

  • Improved FPSCR register display

Libs/Realtime

  • Fixed the version tag

Libs/TTengine

  • Added support for configurable hinting and anti-aliasing mode
  • Implemented RGB sub-pixel anti-aliasing
  • Implemented highly optimized rendering routines
  • Fixed several memory corruption bugs and race conditions
  • Implemented TT_PrintMode
  • Fixed mixed font size issue

Default UI Skin

  • Default Ferox Skin has been replaced by the retro-inspired Origo skin, which had been first introduced in MorphOS 3.10

Devs/Networks/p50x0_eth.device New

  • Driver for onboard GbE controller of the P50x0 A-EON boards

Fonts/_ttf

  • Updated RobotoMono font with correct fixed width information

MUI

  • Account for text format spacing even if the actual object isn't there. Fixed Listtree arrow-text spacing
  • String.mui: Additional checks in OM_SET against trying to do RastPort related computations while not shown
  • String.mui: Fixed a cursor position check
  • Disabled LCD AA for regular MUI text to be consistent between MUIA_Unicode modes
  • Shuffled some early initialisation code around to avoid a random boot hang
  • Fixed Unicode support in register group titles

Network/Netstack

  • DNS resolve operations can now be aborted

Prefs/Font.mprefs

  • Added support for configurable hinting and anti-aliasing mode

Prefs/Preferences

  • Minor UI improvements

Skins/Origo

  • Added some additional sizes to qualify as new default UI theme

Tools/FTManager

  • Fixed a crash with anti-aliased font preview

Utilities/Grabber

  • Fixed to work when Reggae classes are not already loaded

Tools/IWizard

  • Protected Install/Update button against being enabled again while an installation is running
  • Only tries to mount HFS partitions that are writable

Utilities/Multiview

  • Fixed selection of unicode fonts for text and guide display in settings