How do I change the Menu Trigger Layout?

You can change the main Menu Trigger Layout and Style by going to Appearance → Customize  → Theme options → General. 

For the Menu Trigger Layout there are three options:

• Icon Only
• Icon + Text
• Text Only

For the options which include an icon, you can choose its Style:

• Three Horizontal Lines
• Plus Symbol
• Dots & Horizontal Lines

Further readings:

• Personalize Your Site Appearance