error: value "GameTool" for key "Categories" in group "Desktop Entry" contains an unregistered value "GameTool"

[Avasam]

GameTool is part of the spec here: https://specifications.freedesktop.org/menu/latest/additional-category-registry.html

# https://specifications.freedesktop.org/desktop-entry/latest/recognized-keys.html
[Desktop Entry]
Type=Application
Name=AutoSplit
GenericName=Speedrun Auto-Splitter
Comment=Image comparison based auto splitter for speedrunning
Icon=AutoSplit
Exec=AutoSplit
# https://specifications.freedesktop.org/menu/latest/category-registry.html
# https://specifications.freedesktop.org/menu/latest/additional-category-registry.html
Categories=Utility;Graphics;GameTool;ImageProcessing;OCR;Qt

error: value "Utility;Graphics;GameTool;ImageProcessing;OCR;Qt" for key "Categories" in group "Desktop Entry" contains an unregistered value "GameTool"; values extending the format should start with "X-"
ERROR: Desktop file contains errors. Please fix them. Please see
       https://standards.freedesktop.org/desktop-entry-spec/1.0/n       for more information.

https://standards.freedesktop.org/desktop-entry-spec/1.0/n is also not a link that exists

[probonopd]

I think these are the categories it is looking for?

[Avasam]

I think these are the categories it is looking for?

It's also allowing Additional Categories (next page, the one I linked to). It's even doing recommendations when you use an additional category related to a main category you don't have.
Note I don't have any error for ImageProcessing;OCR;Qt

GameTool is probably newer than the last appimagetool update

[probonopd]

You are correct. Is that spec still a moving target? Then you are probably right that this tag is too new.