In the JournalArticle StyleSheet there are useful hot keys Alt+6 for a DisplayFormulaNumbered and Alt+5 for the DisplayFormula. Such hot keys, however, are not present in the Default StyleSheet. Even more, there Alt+5 is reserved for the Section, and Alt+6 - for the subsection styles.
Is it possible to introduce custom hot keys for (generally) any cell style for which there is no built-in one?