The text right above the TTS input box actually states "Note that you can use square brackets for dynamic responses (see documentation for more info)", which works in the exact same way the commands do.
I.E.
You're [quite;] welcome;yes sir
Will randomly speak "You're welcome", "You're quite welcome", or "yes sir".
I'll admit there isn't actually a section in the documentation for "dynamic responses", but the syntax is the same as "Dynamic command sections".