Code might not be compatible with your theme.
See video on what it looks like but follow instructions below on how to implement the code.
1. First, we have to add a Sidebar menu in the Navigation
Go to Online Store >Navigation> Click Add menu.
2. Make sure you write title "Sidebar Menu"
3. Link collections you want to show
4. Click "save menu"
5. Then, we need to go to Online store> Themes> Actions> Edit code>
6. Go to Snippets folder, create a new snippet and name it custom-sidenav. Replace the code below, then click SAVE
7. Replace the code in green to real value.
8. Go to Section folder and open header.liquid. Before </header>, place the code below, then click SAVE