I know there is an option to disable autocorrect for all applications, but how do I disable autocorrect for only one application?
Turn off Autocorrect per Application
You can do this in "Edit" menu for that Application under "Spelling and Grammar" and disable "Check Spelling While Typing".
I want to expand on @Grizzwald's answer as that sadly won't always work.
IF "Correct Spelling Automatically" is grayed out for your Application (which was the case for me using the Todoist app).
- Found here:
Edit->Spelling and Grammer->Correct Spelling Automatically
THEN you'll (unfortunately) need to turn this off for all Applications under:
System Preferences->Keyboard->Text->Correct Spelling Automatically