Vertical Layouts
You can change or customize the left side navigation very easily.
How to add new menu items/change menu items?
                                        In order to add, change or remove menu items from the left side navigation, simply edit in file
                                        templates/layouts/_sidebar.html.twig. The change would reflect in all the html files automatically. 
                                    
How to change width?
In order to change the width of left side navigation bar, open a file 
                                        assets/scss/_variables.scss and change the value of variable 
                                        $sidebar-width. The default value is set to 240px.
                                    
How to use pre-built layouts?
Each of the layout options is provided below with steps you would need to perform:
                                            Light Sidebar
Remove data attributedata-sidebar="dark" body element to have light sidebar.
                                        
                                            Colored Sidebar
Add data attributedata-sidebar="colored" body element to have Colored sidebar.
                                        
                                            Compact Sidebar
Keep your body element with data attributedata-sidebar-size="small" E.g.  <body data-sidebar-size="small"> to have small sidebar.
                                        Icon Sidebar
Keep your body element with classvertical-collpsed" E.g.  <body class="vertical-collpsed"> to have icon sidebar.
                                        
                                            Boxed Layout
Keep your body element with classvertical-collpsed and data attribute data-layout-size="boxed" data-keep-enlarged="true" E.g.  <body class="vertical-collpsed" data-layout-size="boxed" data-keep-enlarged="true"> to have boxed layout with icon view sidebar.
                                        
                                            Preloader
In order to add pre-loader in your page, include following html afterbody element.
                                                <div id="preloader">
                                                <div id="status">
                                                    <div class="spinner-chase">
                                                        <div class="chase-dot"></div>
                                                        <div class="chase-dot"></div>
                                                        <div class="chase-dot"></div>
                                                        <div class="chase-dot"></div>
                                                        <div class="chase-dot"></div>
                                                        <div class="chase-dot"></div>
                                                    </div>
                                                </div>
                                            </div>