Keyboard shortcut to insert text - Keynote I'm new to Keynote and am disappointed by the lack of shortcuts for basic actions like "insert text". Any idea of how to attribute a single key such as the letter "T" to insert text action?

If for any reason a single letter without cmd/opt/whatever modifier key is not recommended, I'm happy with other possibilities..
Have you tried adding keyboard shortcuts through System Preferences? See this article on the Apple Knowledge Base.