Menus > Layers > Delete > Merge duplicate layers

Layers > Delete > Merge duplicate layers

Merges the contents of all duplicate layers into the original, then deletes the duplicate layers.

When you have a series of layers called <myLayer>, <myLayer>#2, <myLayer>#3, etc, the contents of all those layers are merged into <myLayer> and the other layers are deleted.

This tool comes in handy after using the duplicate layers option in Edit > Paste .