My editor has a full fledged Overworld editor, you can modify palettes (there are 4), and set any palette to any of the 16 tiles. You can force a terrain "group" to stop with the bracket tool, so that covers places like the hidden palace 6. Now all attributes on key areas are accurately understood, so you can change all of them, and move the key areas around. The "crosshair" tool lets you select and move key areas, but you can also use the popup menu to select them. This means you can also select them by hand even if you can't see them on the map (an area with Y position 0 is out of bounds). You can use the lasso tool to fill, swap or randomize tiles. You can choose a few display settings, like grid and connections between areas. Nothing about the Demons, which could be a nice addition.
The Side View editor is quite advanced, but it doesn't save yet. You have access to all regions. You can change the association between the data and the area code. This is because more than one area can have the same terrain. Change the enemy group for each area. You can modify objects attributes, add or remove objects, modify enemies, add or remove enemies. The enemy sets can be browsed and selected from another window. You can change the area destinations for each of the four sides. You can also edit all the attributes: background map, no ceiling, extra layers, palette set, tile set, area width. In the Towns section, you can set the destinations of doors.
There's also an editor for Link's attributes: attack power, magic names, costs and effects, and level ups names and experience needed. This one is pretty much like before, except I put everything in the same window, instead of using multiple tabs. Plus some sugar, like the attack power differentials for each level. This shows how Link is going to progress as he levels up.
The enemy editor is quite interesting, you get to change all attributes (steals points, immune to Thunder, etc.), the experience code with the master experience table in the same window for reference, which can be modified too. You can change the item type given by the enemy (no item, minor and major). You can also change the damage code of the enemy, and again the damage table for reference, editable.
The text editor still only covers the Towns (no intro or ending), but all 98 dialogs are there. The new feature is that you have a picture that shows exactly how the dialog box will appear in the game, using the graphics from the ROM. There is also the Game Data editor, which contains various data, like beginning values: spells, items, techs, heart/magic containers, lives, crystals. Also, number of enemies to defeat for item, change the health below which it starts beeping, or cancel the beeping completely. Also, the amount of life restored by the Life spell. I could add quite a lot of miscellaneous stuff in there.
I started working on a tile editor (for the Side Views), which lets you edit what tiles are used for objects, the four 8x8 tiles that make the tiles used in layout, tiles palettes, and I will eventually add a way to change which tiles are solid and which aren't. You can see all of this in pictures in this old thread : http://www.romhacking.net/forum/index.php?topic=22077.0
It's been quite some time. I'm just back from a long dry spell of ROM hacking, so that's why the thread is that old. You can see a screenshot of the tile editor, and some of the "latest" progress.