This tool first prompts you for the base mtext object, then repeatedly asks for a pick on the mtext object to join. The text from the second mtext object is appended to the base, and the second mtext object is removed.
Keyboard Command: MtxJoiLin
Keep in mind that the width of the base object will remain in control. After joining all desired mtext objects, you can adjust the width of the new paragraph as desired.