Apple - Change tabstop in TextEdit.app

For plaintext tabs, you don't need to replace the entire TextEdit app to change it. I looked at the source code and it provides the simpler answer: Open the Terminal and type

defaults write com.apple.TextEdit "TabWidth" '4'

Where '4' is the number of spaces a tab should be.

Yes.

1. Make sure Format > Text > Show Ruler is enabled.
2. Locate the tab stops in the ruler (Fig. 1).
3. Move the first one to 1/4 inch (Fig. 2).

Alternatively, you could use something like Keyboard Maestro, TextExpander, or BetterTouchTool to map four spaces to the Tab key. This is the only way I'm aware of to do it for plain text files (.txt).