Root Settings Folder bug in PT12
You can change the Root Settings Folder in Operation Preferences and when saving a preset from a plugin (like Avid Trim), it saves it in the correct folder. HOWEVER, it does NOT show up in the list of presets until you close the session and re-open it.
This bug is in Pro Tools 12.4 and quite possibly other versions. I seem to recall it's been broken for quite a while.