Is it possible to duplicate mapping groups from one channel to another?

This is not possible. Because every marketplace has its own data model (which defines which data is wished and mandatory) we cannot duplicate mapping groups to another channel.

It is possible though to re-use certain mappings you made earlier. If you, for example, once mapped the color 'blue/red' to 'multicolor', EffectConnect will recognize this the next time it needs to map the color.