In fact, it's very easy if you know the sequence of monsters.
I suggest you make a backup file before modify, because it's easily to error.
And you should know about "pointer" in programming language.
Now, we can start...
Because FlyingSB is an old game, the data in memory address is always the same.
So, you can find the string of monster's name easily.
Chinese literal is stored by ASCII code, maybe Korean is the same.
In UE(or others), use ctrl+F , and enter the monster's name which you want to modify.
Here I use "牛魔王" in chinese version.
In Chinese ver FlyingSB.exe, it's look like this:

and the result is like this:

You can find the start address is "0x29CB40H", this will be a target of some pointer.
If your monster has more than 1, it meant different monster.
e.g "那印" has 2, it meant you will fight he 2 times, first is in the 트랄록 동굴,second is in the -마탑- <손오공 쪽>.
The pointer will be "40 CB 69" when running game. It is the address plus "400000H" and reverse.
Use ctrl+F to find "40 CB 69":

You will jump to another screen like this:

In the area, it's is the data of monster "牛魔王".