Some more editor suggestions...

General Functionality

* NPC Faction Change on Dialogue Completion: Sometimes you really want an NPC to go from friendly or neutral, straight to hostile.
* Option to Strip Players of Gear: Possibly a controversial one, but starting players out stripped of gear for a module (if this option is set, the module should say so in order to avoid issues. Like a prompt saying "You will be stripped of your gear joining this module"
* DM Abilities: Sometimes you want, as the DM, to heal, buff or debuff your players. Heck, sometimes you want to heal your monsters. Gifts from the gods, to one side or another. One of the great things about being able to debuff players is acting as curses, saying the enemy has injured them, etc.
* Map Duplication: Make a map, duplicate that map, and change it from there. Why is this useful? Say you have a city. The players leave this city. Later they come back to the city. It has been attacked by raiders. You want to be able to take what you had and make a destroyed version. Doing this from scratch can be problematic, especially if your memory sucks.
* Pitch Black Atmosphere: Some dungeons don't have any light sources other than the doorway. Sometimes they don't even have that if you go deep enough. This would be huge for creating suspenseful, nerve-wracking maps.
* Ability / Class Checks Matter: While dealing with Branching Dialogue, we'd love to be able to set up inherent ability checks in to conversations. Not just ability checks but class checks as well. For example, you may be able to talk your way out of a potential combat scenario with a charisma check. Maybe you can help someone with a problem by being a Wizard. Maybe certain quests will only be available to Rogues, or someone with a high intelligence. Perhaps you can pseudo Sense Motive with Wisdom to tell that an NPC is holding something back, opening up a Charisma check option to get them to spill the beans. There is a huge amount of things a good DM can do with this.
* Populate Area with NPCs: Right now we have to create every single NPC for a town ourselves. What would be nice is the ability to quick populate a town without needing to create every, single towns-person, craftsman, farmer, villager, etc. Could be a creature set.

Quests

* Custom Quest "Story Items" - Basically just an "inventory icon" name and description. So we can create quest-related items: Purple mushrooms, Troll Thumbs, Historical Tomes, Orc Tribal Necklace, etc.
* Randomly Dropped Custom Quest Item From Killed Mob: Some people do want to be able to set up quests like "Collect 3 Spider Venom Sacs". Unimaginative, but sometimes a necessary evil for questing. Sometimes an NPC REALLY does need those monster items for something important. Sometimes it's just a random side quest. Sometimes it's a random side quest that could be important later, if you completed it. Either way, a useful addition to questing.

Ambience

* Disable Lights: Torches, window lighting in cities, etc. Sometimes you want an abandoned city only lit by moonlight.
* Placeable Point Lighting: Perhaps there is a light coming from the ceiling (through cracks or holes) and you want to aim them at specific places, or just fill your dungeon with random lighting from various sources. Heck, maybe all you want to do is extend the existing light sources. Adjustable radii are useful.
* Selectable Music Per Map: We'd like to be able to set a maps various music instead of having it all chosen for us. Area Music, Battle Music, etc. If you guys have various tavern themes, we'd love to play them in actual taverns we create. Either repeats a single track or cycle through tracks we choose. Both options would be nice. You guys gave us the tools to create atmosphere with lighting and various effects, let us do it with music too.
* Placeable Sound Effects: Sometimes you want to hear running water in an area, because running water is nearby. Or dripping. Or squeaking. All sorts of things can be done here.
* Overhead Announcements: Maybe you want the players to know there is a massive attack happening somewhere. People don't have to use this, but some want it.
* Placeable Visual Effectsnt: Smoke, fire, glowing magic pixie fairy rings, dripping water, waterfalls, water planes, lava, etc.

Other

* More Humanoid Armor: Weapons and shields are nice, but we could really use the ability for humanoid monsters to be able to change armor. Weapons and shields are nice, but some creatures could have different armor types (ESPECIALLY humanoids). It'd be awesome for making NPC factions a thing. Selectable hairstyles would also be nice for some creatures (like Goblins.) Variant enemies are nice and all, but we could definitely take it further with some species. Being able to apply scars and whatnot to monsters can help when making a unique version.
* Large Color Selection: We don't even have fluorescent pink for our Ogres to disguise as pretty pink princesses. This makes some of us sad. Not many dark options currently. Lots of brights.
* NPC Patrol/Waypoint/Paths: Sometimes you want enemies or NPCs to walk around. Maybe you want them to patrol. Maybe you want them to go to a specific place. We can't do any of this right now. Monsters included. Sometimes you want the NPC to flee after having a conversation with the players, such as if you free them from a cage and they thank the players. You wouldn't want that NPC to stick around (It needs to be doable DM-less so the DM can focus on other things. Not all of us are amazing micromanagers.) Another thing that would be very useful is having NPCs run up to players for a conversation. Maybe you want to set up a side-quest that is given that way. It all makes the world feel more alive!
* NPC Wandering: Towns can be an incredibly stale environment when NPCs are all standing around doing nothing. Sometimes you want your non-important NPCs to walk around. Heck, sometimes you want your IMPORTANT NPCs to walk around. Sometimes you want that lawkeeper to survey a crime scene. Sometimes you want townsfolk going about their daily lives. This would do wonders for making much of a campaign feel more alive. Monsters included.
* Better Control of Aggro Radius: Sometimes you want an enemy to see the player the second they're on screen (as long as there is line of sight). Sometimes you don't want them to see players until they're right up against the characters nose. Maybe the enemy is blind.