How to sync changes of metrics in master to layer?

Glyphs
1

I’m trying to find a way to sync the changes that happen in the master layer to reflect in another layer of that master.

This will be helpful in a case such as using Bubble Kern.
For example: if +10 is added to the LSB of the Master layer then the Bubble layer will also automatically add +10 so that they will be in sync.

Is there a plugin or custom parameter that does this?

2

Currently not, but you can define a shortcut for switching to the next layer and repeat the operation.