Different size font in the same text box

Hello 

Apologies in advance for posting a most basic question. Last time I built a SS site I using an older template  and I distinctly remember that you could use multiple text sizes (eg. h1 with p2) in the same text box. Was I imagining this? I've tried to mix text sizes in the latest version of the Clarkson template and no matter what I do it always converts any text in the box to the same style eg. if I choose p2 all text in the box is formatted like this. 

Any pointers would be most welcome 

Thanks!    

Do you use any custom code? If not, can you take a quick video when you edit text & link to your site, we can check easier