How to Lump Multiple Layers?

Use the Set_Input_Layer_Map command to map layers in the GDSII file to layer numbers you want.
e.g. If you know the GDSII file has layer 6,9,10 and you want them all to be 10, then do this: 


Now all data on layers 6,9,10 will be treated as data on layer 10.
Use Set_Input_Layer_Map BEFORE opening a file. And do not change it's settings until the next file is opened.
You need to know what layers are in the GDSII file before you open the file.