In Kate text editor, one can auto complete using either the Tab or the Enter key.
I find auto-completion with the Enter key disruptive, because often you really do mean what you say, and want to go to a new line. Who knew.
How can I disable only the Enter key auto-completion without removing the Tab auto-completion?
You CAN'T do that.
From https://bugs.kde.org/show_bug.cgi?id=316413:
Sorry, but auto-complete really works ok the way it is. If we alter that behavior, we will get many more reports about that than with the current way.
And then:
You can deactivate the auto completion in the settings. Then you can invoke it manually. If that doesn't help, then yes, Kate is perhaps not the best choice, sorry.
So it seems, from the developers' own mouth, that Enter can't be turned off. You can turn off autocomplete as a whole, or if you don't like that, you can find another text editor. Or you can edit the source code yourself, after all it's Open Source.
The developers like it as it is, and have no intention of making the behavior configurable.