What does that mean?​ 'M', 'E'

E (edited) means you have changed one or more parameters of the Rig, compared to the Last Saved version of the Rig.

And M means the parameter has been Morphed.

Quote from lk_bill

And M means the parameter has been Morphed.

Or more accurately that it has been "armed" for morphing, right?

Quote from Michael_dk

Or more accurately that it has been "armed" for morphing, right?

Well, shouldn´t it then say "A"??
....just kiddin´

Quote from docmidnite

Well, shouldn´t it then say "A"?? ....just kiddin´

sorry - I meant to say it has been Made available for morphing

The "M" indicates that a morph value has been set for that parameter.