t so that tab characters are used for indentation by default. AUCTeX apparently changes the value of
nil and uses some other system for handling leading indentation, and there are many customization variables in the groups "TeX Indentation" and "LaTeX Indentation". As far as I've found so far, these variables only allow you to change the number of space characters used for indentation. How can I configure AUCTeX to use tab characters for indentation?
AUCTeX doesn't use tabs at all for indentation. This is done by changing two variables:
indent-line-function. Thus, in order to get tabs back you can restore the default values of these variables (
t for for the former and
indent-line-function for the latter). You can do this in your init file with a hook:
(add-hook 'LaTeX-mode-hook (lambda () (setq indent-tabs-mode t indent-line-function 'indent-relative)))