How to merge layers in illustrator?
On the Links tab, click the context menu button -> Flatten Layers
Copying and merging layers
You can get a new layer by copying an existing layer. The Duplicate Layers menu command in the Layers palette creates a new layer over the active source layer, copies all its layers, groups, and objects, and saves all its settings.
You can also copy a layer by dragging the layer line onto the Create New Layer ( ) or Create New Sublayer ( ) buttons at the bottom of the palette.
You can reduce the number of layers by merging those that can form a whole. To merge two or more selected layers, you have to run the Merge Selected command on the palette menu.
The contents of all merged layers are moved to the active layer or group. It is desirable that the active layer or group are not fixed or “hidden”, as the program will be “forced” to move all objects to one of the available layers or to one of the available groups. In the example in Fig. 9.6, the program does not merge into the active layer Layer 2, but into Layer 4, because Layer 2 and Layer 1 are hidden and fixed, and Layer 4 is the only one available.
If you merge layers that are arranged in a split, it is necessary to pay special attention to the result, because merging such layers may change the overall pattern.
Using the Collect in New Layer command of the palette menu, you can collect all the selected layers, groups and objects on a new Layer 5 (fig. 9.7).