Envelope Symmetry is a tool that helps creating and maintaining perfectly symmetrical envelope setups.
Like in Armature Symmetry one side is taken as reference. Create or modify only the reference side of the envelopes. The opposite side envelopes will be automatically created or adjusted.
The side the envelopes belong to is determined by the bone they are attached to.
If the envelope name (containing the configuration of the bone and weight) gets changed, it will also get automatically adjusted.
To be continued...