Hello @warren_hawkins57R37,
I hope you're doing well. If you look at the reference for the layer command, there are mirrorable pairs of user layers which you can use for application that require the mirror behavior. Those layer pairs are
This is supported for the layer pairs 53/54, 55/56, 57/58 and 59/60. It should be used with care regarding later EAGLE versions.
See here for more details
https://help.autodesk.com/view/fusion360/ENU/?guid=ECD-CLI-L#layer
Let me know if there's anything else I can do for you.
Best Regards,

Jorge Garcia
Product Support Specialist for Fusion 360 and EAGLE
Kudos are much appreciated if the information I have shared is helpful to you and/or others.
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