KTabs costs $30 which is kind of ridiculous. So here's a free option.
To use the application, simply download the KalimbaTabCreator.app, then double click the icon.
Application will look like this:
To add a note, just click the appropriate square, and a black dot will appear. To erase, just click again.
To add additional measures, click on the Add Measure button.
To save your progress, use the Save button. Your song will be saved as a text file. To best read the text file, use a text editor with a monospace font.
You can load a previously saved song by loading the text file using the Load File button. WARNING: doing so will overwrite any current progress.