You can set a custom plug-in map as the default map for a plug-in, instead of the Factory Default map.
When you set a custom plug-in map as the default, it applies across the entire session. All instances of that plug-in that were set to the Factory Default map, or to another custom default map, change to the new default.
If you change parameter mapping in the custom plug-in map that has been set as the default, the changes will propagate to all instances of the plug-in using that default.
Default map settings are stored as global (system-wide) Pro Tools preferences, so they are applied to all sessions that you subsequently open or create on that system.