Since Golden Egg is the standard for Yoshi's Island hacking and there isn't a proper Layer 3 documentation or tutorial, I decided to remake the document made by Yoshis Fan for EggVine, but with GoldenEgg strings and settings, and adding more useful information. Credits to Yoshis Fan itself, and to Raidenthequick and Mattrizzle, who helped indirectly with useful complementary information.
-Fixed some wrong values
-Fixed some values that were still on decimal instead of hex
-Added some missing Sprite values
-Added some information of Unused and Duplicate Palettes
-Backgrounds and Sprites are now separated of each other
-Re-organized the Sprite section to be clearer
-Fixed information of unused layer 3 backgrounds E and F
-Fixed minor grammar and some cells' size
I'm already working in a web version of this, with pictures and more organized info, just in the case you didn't know. This document was just intended to obsolete the old Yoshis Fan version which is wandering in the YI and SMWCI forums.
Some grammar/spelling issues and a bit of weird formatting aside, (you could probably move some stuff off into new columns instead of just cramming it into the "Effects (and extra notes)" column) I'm going to go ahead and improve this. The information inside appears to be accurate and it's an improvement on the earlier version that's on the site.