I've been playing around with this command I found recently online. You can use it to set players or mobs to your extended target window, if you know their name, and if they are in the zone and within range.
I'm thinking about using this as my method of adding tanks/healers to my ext target window for healing/rezzing/buffing on raids. Other people may find this useful for putting mobs in a certain order, or healing pets and etc.
Notice on this, players do not require the numbers at the end of their name, but mobs do, even pets! It's my understanding the first mob in the zone always has the numbers 00, it increase for every same name mob in the zone.
With 3 hotkeys you can set your entire extended target window. You'd have to edit each event as MTO changes, and people come/go. But it helps for when adding tanks that haven't zoned in yet. It makes it easy to just click the button once they zone in and add them instantly into the correct location on the MTO.
You can even add wards (like shaman/druid/cleric), or traps!
Still working out how that might be beneficial, besides seeing when they despawn, or using wards as a central location to bounce splashes.
Also can make a key for adding the raid assist's target to your extended target.
/xtar set 1 raidassist1target
/xtar set 2 raidassist2target
/xtar set 3 raidassist3target
Raid mark to ETW commands
/xtar set 4 raidmark1
/xtar set 5 raidmark2
/xtar set 6 raidmark3