One thing I've noticed: If, when editing the condition set list, you are at "1" and hit (down), FF4kster crashes (like it's trying to go to "0," but then realizes there is no 0 and self-destructs). Not a big deal if you're careful, but could cause loss of a lot of unsaved data for someone who's not careful.
I can fix that Fixed
A small suggestion: When selecting the monster's size, would it be possible to have the editor say, for instance, "4x4" instead of "1?"
It certainly would, but I would need a list of what size indexes correspond to what dimensions
A question: Wasn't there a plan to have the ability to edit monster formations as well? Please don't interpret that at all as disappointment - monster formations are a blip on the radar compared to what you've created here.
There was and still is. It will be separate from the monster editor though. In fact once the monster editor is a little more debugged the formation editor will be next.
Also, I don't recall the Features (apparently previously Item Ranges) option in previous versions. Did I miss a version somewhere along the lines, was I simply not paying attention to what was there, or is this new?
It was in the previous version.
Still need to do some more testing to see how things work in actual gameplay once changes are made, but so far it looks great!
Thanks, and thank you for pointing those out!
Very nice to see this available. One thing I've noticed so far: If you hit tab to edit a reaction sequence, going back with esc will increment its index by 1.
I can fix that Fixed
Also I don't seem to be able to toggle the boss bit off on monsters it's already set on. Can turn it on and off other monsters fine.
I can fix that Fixed
Immune in weaknesses should be "very weak" or something similar.
The thing there is that it's reading the element names from a config file, and also it's using a stock menu component that is used for all element/status menus without regard to what launched it (whether it's relating to weaknesses or resistances or whatever). If you don't like the name you're certainly free to go into the config file and change the word "immune" to something more general-sounding.
Attempting to add elements to monster attacks sets statuses in the second column instead.
I can fix that Fixed
I think you need to work on memory usage, it increases every time you move the cursor over an option, and this adds up really quick when viewing monsters. Just scrolling down the entire list without doing any editing increases the memory used from about 8 megs to 391. I had it using over a gig at one point through fairly normal viewing and editing. 
TBH I never really looked at the memory usage. Is this something specific to the monster editor or does this happen just using the tool regardless? In any case it sounds like there's some kind of memory leak somewhere. I'll see what I can do.
Lunar scripts don't seem to be loading for me either.
Ah yes I forgot to mention, that is a known issue. Until I'm able to determine which monsters appear on the moon and which ones do not, they're all just going to have the regular scripts. Soon I will go through the monster list and create a config file that says which monsters are on the moon, but this will simply be a stop-gap solution until there's an actual encounter list editor, whereupon FF4kster will simply read from the encounter information which monsters appear in lunar areas, and show lunar scripts for those and regular ones for the rest.
Incidentally, behind the scenes it actually is loading the lunar script data, and even saving it, just there's no way to edit it currently.
Again, thanks for pointing those out!