save Decal

If you save it as a p2d file you can just drag and drop it out of the task pane (like the the stock decals).  You don't have to browse for it, etc.  If it's something you use all the time it will save you time.

The p2d files store extra information regarding the decal such as whether it uses the underlying appearance, or other appearance properties. Like Rob said, it means you don't have to tweak these settings every time you want to use the decal.

They're actually pretty simple little files, if you edit one in notepad it has info like this:

color texture "decal_image_tex" "Images\textures\decals\sw_logo_lets_go_design.jpg"

 

     "swP2D"  on ,

     "useUnderlyingAppearance"  off ,

     "diffuse_factor"  1 ,

     "specular_factor"  0 ,

     "specular_color"  1 1 1 ,

     "roughness"  0.002 ,

     "reflectivity"  0 ,

     "mtl_ior"  0.5 ,

     "transparency"  0 ,

     "blurryReflections"  off ,

     "doubleSided"  on ,

     "refractionRoughness"  0 ,

     "luminousIntensity"  0 ,

     "initTextureWidth"  0.1524 ,

     "initTextureHeight"  0.041656 ,

     "masking_mode"  0 ,

     "invert_mask"  off

Note, as you can see above, it does not REPLACE the source image, only links to it.

I would also suggest saving the decal as part of the file to avoid losing the reference in case the files are relocated.