Hey all,
 
I remember this coming up before and I didn't think it would work but somehow I remember being proven wrong - can you move mix scenes between projects? I did a bunch of rehearsal recordings with all of the same instruments and channels and mostly gains too. I started all of them from a template that I created beforehand but started each rehearsal date with a fresh project. Now I started some basic mixing on the first project and I would love to be able to save that mix and apply it to the next project. Can this be done? Or is it a rather convoluted track templates kind of situation? I don't see any way to export/import mix scenes. The projects are even all in the same folder which has a subfolder called 'Mix scenes' but I can't seem to get to them from the new project.

In your projectfolder is a folder called "MixScenes". There are the files generated as mixscenes.
Try to copy this files to your projects. Maybe this works.

As I said the projects are already in the same folder. This doesn't seem to do anything.

You must have each project in an own folder.
I just tried to save a mixscene in a project to file (in my case K19443-Mix(2).cwm). Then I openend an other project and dragged my mixscene file from the windows explorer (K19443-Mix(2).cwm) into the trackview from an other project. The fader moved all immediately to the values of the first project.
Maybe this is the reason for you. Generate your mixscene to a file and drag and drop it (from windows explorer) into the trackview to your other projects.
Possibly this only works, when you have each project in an own folder. Because Sonar must create its own local mixscene file. Otherwise files will be mixed and confused.

It is not necessary to have each project in a separate folder. The project name is part of the mixscene file name. In the media browser, navigate to the mixscene folder (I get there by using the "Project Audio Folder" in the media drop down then up one level and click the MixScenes folder) and drag the mixscene onto the project. If you wish to have a separate mixscene for a project use "Save As New Scene" in the Mix Recall module and the new mixscene is created in the MixScenes folder using the current project name.

I would basically work with separate folders. If you want to open a project in 3 years you have a mess in the backups of your audiofiles when all is in one folder.

There is a difference between

THambrecht
You must have each project in an own folder.

and

THambrecht
I would basically work with separate folders

The point being there is no separate folder requirement to perform the task the OP wants. How one chooses to archive projects for future reference is a different matter entirely.