Any way to add text boxes (and font size) all at once across multiple slides?

Using Sequoia 15.0.1 in a MacBook Pro (along with multiple help resources...). Have found the only way to add text to slide photos is to individually add a text box via Edit Tools/Markup/Text box. Unwieldy. There's got to be a better way, but haven't found it. What am I missing? Help appreciated.