Improvements

[dl-tg]

You should really improve this.

Firstly, the text speed is way too slow.
Secondly, the faces are poorly scaled. Usually you multiple the scale by 2 if you get the smaller ones directly from Undertale itself.
Thirdly, make key mappings for both Z and Enter, X and Shift. Enter and Shift aren't used as much as Z and X.

The text font also seems to be weird.
Papyrus' and Sans' font size in Godot should be 32 pixels, same with Menu (Determination Mono) one.
Try disablig anti-aliasing?

Adding heart and label for each option in the editor seems to be kinda absurd. You can do all of this with one Text scene and player's heart with for loop.
The code also seems to be bloated. I can imagine doing all of this but with result code being 2-3 timer smaller and easier to read. If i was you, i would entirely rewrite it.

When I open the game, i see this:
Cannot open file 'res://Maps/Ruins/../../../../Unitytale/Assets/Maps/Ruins/Ruins1.tsx'. Error opening TSX file 'res://Maps/Ruins/../../../../Unitytale/Assets/Maps/Ruins/Ruins1.tsx'. editor/editor_file_system.cpp:1759 - Error importing 'res://Maps/Ruins/Ruins_Grave.tmx'. Cannot open file 'res://Maps/Ruins/../../../../Unitytale/Assets/Maps/Ruins/Ruins1.tsx'. Error opening TSX file 'res://Maps/Ruins/../../../../Unitytale/Assets/Maps/Ruins/Ruins1.tsx'. editor/editor_file_system.cpp:1759 - Error importing 'res://Maps/Ruins/Ruins_Grave.tmx'.

I also see a popup that tells me that an addon is broken (Godot TIE)... for what godot version is the project?
600 lines for a text writer seems to be overly exaggerated. Some variable names are named confusingly, making it even harder to understand the code. You should name and if you have to - comment them properly, since this is an open source product.

The filesystem is confusing. Why is there fonts, audio and game scripts in addons folder? Why is there scripts in Music folder? What is the name supposed to actually mean?

Always set Filter boolean to false when importing sprites for a pixel 2D game.
There's some more problems but those are the main ones.