The scroll part is Bootstrap's ScrollSpy component. To customize the style of the active
link can be easily done with a little CSS..
/* hide sidebar sub menus by default */
#sidebar.nav .nav {
display: none;
font-size:12px;
}
/* show sub menu when parent is active */
#sidebar.nav>.active>ul {
display: block;
}
Bootply demo: http://bootply.com/109952