Add the following code to extra.less:

Let me know if you need specific modifications!
CSS:
.offCanvasMenu--nav a[data-nav-id='whatsNew']:before,.p-navEl a[data-nav-id='whatsNew']:before {.m-faContent("@{fa-var-question}");color: #faf08c;}
.offCanvasMenu--nav a[data-nav-id='members']:before,.p-navEl a[data-nav-id='members']:before {.m-faContent("@{fa-var-users}");color: cyan;}
.offCanvasMenu--nav a[data-nav-id='xfrm']:before,.p-navEl a[data-nav-id='xfrm']:before {.m-faContent("@{fa-var-download}");color: #ee5f78;}
.offCanvasMenu--nav a[data-nav-id='xfmg']:before,.p-navEl a[data-nav-id='xfmg']:before {.m-faContent("@{fa-var-camera-retro}");color: #93f8fc;}
.offCanvasMenu--nav a[data-nav-id='xa_showcase']:before,.p-navEl a[data-nav-id='xa_showcase']:before {.m-faContent("@{fa-var-planet-ringed}");color: #db52db;}
.offCanvasMenu--nav a[data-nav-id='xa_ams']:before,.p-navEl a[data-nav-id='xa_ams']:before {.m-faContent("@{fa-var-pencil}");color: #bdf406;}
.offCanvasMenu--nav a[data-nav-id='xa_cas']:before,.p-navEl a[data-nav-id='xa_cas']:before {.m-faContent("@{fa-var-dollar-sign}");color: #04cf04;}
.offCanvasMenu--nav a[data-nav-id='xa_ld']:before,.p-navEl a[data-nav-id='xa_ld']:before {.m-faContent("@{fa-var-link}");color: #9c95c6;}
.offCanvasMenu--nav a[data-nav-id='xa_rms']:before,.p-navEl a[data-nav-id='xa_rms']:before {.m-faContent("@{fa-var-atom}");color: #9c95c6;}
.offCanvasMenu--nav a[data-nav-id='xa_ubs']:before,.p-navEl a[data-nav-id='xa_ubs']:before {.m-faContent("@{fa-var-blog}");color: #f4b4fa;}
.offCanvasMenu--nav a[data-nav-id='xa_ims']:before,.p-navEl a[data-nav-id='xa_ims']:before {.m-faContent("@{fa-var-clipboard-list}");color: #9c95c6;}
.offCanvasMenu--nav a[data-nav-id='tl_groups']:before,.p-navEl a[data-nav-id='tl_groups']:before {.m-faContent("@{fa-var-user-friends}");color: #a5f4ae;}
.p-navEl [data-nav-id='astroutil']:before {.m-faContent("@{fa-var-tools}");color: #fd9ab0; display: block; text-align: center; margin-left: auto;
margin-right: auto; padding-right: 30px;}
.offCanvasMenu--nav [data-nav-id='astroutil']:before{.m-faContent("@{fa-var-tools}");color: #fd9ab0;}
/* Navtab menu using FontAwesome 5 */

Let me know if you need specific modifications!