Yes, Version 1.1 supports importing custom palettes directly from Lospec

To use them, just download the .hex(preferably)  .pal, and png image format. drag and drop the file directly into Lospec Palette button. 

About the custom workflow:  Currently you can't create a  "fully new" custom palette from scratch. The starting point is always your original image. From there, you can:

• Color Reduction and applying the presets
  
• Lock Colors: Pick up to 10 specific colors you want to keep exactly as they are in the preview.
• Delete Colors: Pick up to 10 colors you want to strip out when lowering the colors in the image.
• Swap Colors: Replace colors you don't want with one from your indexed palette. This part is a bit finicky right now, but I’m planning to make it more intuitive soon.