How to make a palette using solid color layers

[AngelH]

I have layers with single color layers as I really like these colors.

I want to make a palette from these colors.

I've followed the instructions at https://docs.gimp.org/en/gimp-palette-dialog.html#gimp-palette-new

I made sure all of the color layers were visible

I selected ALL

Import Palette

Chose

• Sample merged: When this option is checked, colors are picked from all visible layers. If unchecked, pixels are picked from the active layer only, even though not visible.
  
• Selected pixels only: As the name says, pixels are picked from the selected area only, in the active layer or all visible layers according to the status of the previous option.
  

Here are the settings I used.
You can see several of the visible layers

And you can see the palette only has one color in it.

Help would be appreciated. I have over 180 layers and don't look forward to color picking each one in order to create a palette.

Thanks,
Angel