It’s here. Copy the code and paste it into a new text document and save it as MXAO.fx
It was removed from the Legacy shader pack on 2nd June 2022. You can still find anything that has been removed if you spend time going through the commits on github.
Please, please, please get into the habit of making backups of all your ReShade installations each time you update. You never know when a shader is going to be rewritten or removed completely. I’ve got backups stretching back to ReShade 0.12. It means you’ll always have whatever you need right at your fingertips.
To backup your current ReShade installation:
Eventually you’ll have a nice collection of old installations that you can go to for old shaders, or if you ever want to revert to a previous version.
Tip: to install an older version from one of your backups you don’t need to run the installation exe tool, you just need to drop the files you backed up into your Bin folder (after removing the ones you currently have installed). That’s it. Easy!