I’d like to revive Cadalyst CAD Tip #3761, contributed by David Shultz. I use the LayMrg command quite often for a quick drawing cleanup, and I recently discovered a new way to implement this command using the Layers palette.
Select the layers you want to merge from the Layers palette. Right-click and select the Merge Selected Layers option; a dialog box will pop up showing available layers to merge into. Select the desired layer. Next, a dialog will appear verifying your selected layer to merge into.
I use the sorting options in the Layers palette to my advantage: sorting by color and merging similar layers in bulk to create a more manageable number of background-per-discipline layers (by name). I also make a delete layer and sort by off or frozen layers, merge into the delete layer, and use the LayDel command to say goodbye to those off and frozen layers for good.
On a side note. I have noticed that LayMrg does not work if you have any locked layers in the drawing — kind of inconvenient, but if you know the rule, you can work around it.
Notes from Cadalyst tip reviewer R.K. McSwain: Layer Merge continues to be a great command, and it was made even better when it was integrated into the Layer Manager starting in AutoCAD 2014. Use caution when using this command in Civil 3D, however, because it is possible to remove layers that are referenced in various Civil 3D settings and/or styles, resulting in drawings errors.