This works without any complications! Did you toggle the "1T/4T" switch (= last icon in the vertical tools panel)? This icon switches from breakpoint-wise/global text formatting.
Yes, I did. The size seems to be holding now per breakpoint, but if I do a hard return it breaks the line at that point on every breakpoint.
Yes, that is expected behaviour. A return is a modification of the text content, not a modification of the text attributes.
In this case you have to choose a different solution:
• Hide the text box, which you want to modify, in this breakpoint (right click onto it and choose "Hide in Breakpoint".
• Place a new text box (or a copy of the first one) with your changes, right click onto it and choose "Hide in other breakpoints.
Thank you! I figured it was something I was doing wrong