“garnicht” is a common German spelling error.
The standard spelling is “gar nicht.”
Example
[Strophe]
Das ist garnicht wahr[Strophe]
Das ist gar nicht wahrThe fix
In the workbench this finding carries one control, labelled Replace with gar nicht. The change is contextual, so it is previewed as a diff in your document first and applies only when you confirm it.
Source
The guideline this rule enforces, as cited on every finding it reports:
Häufige Fehler und Falschschreibweisen verified Common German misspellings, including garnicht and nähmlich