Hello,
To make your portal button available in menu offcanvas, I have duplicate your menu portal site module and rename it to Menu-portal-btn-mobile and assign position to offcanvas, Please, Check screenshots,
Then I add this css in template options -> Custom code -> Custom css:
@media (max-width: 991px){
.offcanvas-menu .offcanvas-inner ul.menu>li ul.menu-child {
display: block;
}
#sp-header #sp-menu .sp-module {
display: none !important;
}
header#sp-header .container, header#sp-header .container-inner {
width: 100%;
margin: 0;
padding: 0 20px;
max-width: 100%;
}
.offcanvas-menu .offcanvas-inner {
display: flex;
flex-direction: column-reverse;
}
.offcanvas-menu .offcanvas-inner div.mb-4 {
order: -1;
}
.sp-module.portal-mb a {
display: block !important;
}
.sp-module .menu,
.offcanvas-menu .offcanvas-inner div:nth-child(2){
margin-bottom: 0 !important;
}
}
Thanks