Having difficulty opening crystaltile2 as well.

About the dialog prompt & level editor - if it's FF6LE we're talking about, then no... it cannot do any changes to the event code itself, which is what dialog boxes and pretty much everything else that takes place during the game includes. There exists however nowadays another utility that includes a level editor, along with a helluva lot of other features, made by Everything called FF6Tools, which is browser based and can do event editing. I'd recommend using it instead of doing it the more tedious way, which is via a hex editor... it'd be a lot more user friendly I'd imagine if just starting out, although I'm sure there'd be a bit of a learning curve involved. It includes the entire 'event script' so you can search for whatever you'd like to edit (Ctrl+F) by searching for a specific line of dialog or what have you, then edit away.
FF6 Tools thread: https://www.ff6hacking.com/forums/thread-3321.html

This is assuming the ROM you are intending to use it with doesn't have a bunch of relocated and/or expanded data etc.

The other option would be to do it the good ol' fashion way, with a hex editor and referencing the 'event dump' document, which you can find here on the wiki along with a few other helpful event hacking infos: https://www.ff6hacking.com/wiki/doku.php...s:doc:game
This way is simple: locate the event code you wish to change with the event dump.txt, and then going to that offset in hex and making it happen lol.