In Flexitive, there are multiple ways to resize a text box depending on whether you hold modifier keys like Shift or Option/Alt while dragging. 

• Resizing by dragging from a corner or an edge does not change the font size in the text box while allowing you to adjust the bounding box and line breaks. 

• Resizing while holding the SHIFT key keeps the aspect ratio of the text box while resizing your text. 
  
  

• Resizing while holding the OPTION key on a Mac (or ALT on Windows) does not change the font size while allowing you to adjust the bounding box from the center of the element. 

• Resizing holding both SHIFT and OPTION maintains the aspect ratio of the bounding box while also resizing from the center.

Learn how to Style your Text.