NLA Editor with Material Key-frames

I’m new to the NLA Editor. I’m seeing how the actions in the NLA Editor refer back to the same actions as in the Actions Editor.
So, I tried key-framing the transmission for the material I was animating. I realized, I don’t know how you would “stash” or “push down” this sort of animation data. This information shows up in the NLA Editor, but it’s not editable. I’ll include a picture. Could somebody help clear up what’s confusing me.

Edit: So i figured how to push down the information so that it becomes editable. But I’m still curious, If the actions are stored in the Actions Editor, where is the key-frame data for materials stored?
Edit 2: It seems to me like the data is stored in the dope sheet and nowhere else essentially. “Start editing stashed action” and “start tweeking strip action” in the NLA Editor both end up opening up the dope sheet.