Versuch das mal:
_header.scss
@include media-breakpoint-up(sm) {
.header-search-col {
.collapse:not(.show) {
display: none;
}
}
}
@include media-breakpoint-up(lg) {
.header-search-col {
.collapse:not(.show) {
display: block;
}
}
}
header.html.twig
{% block layout_header_search_toggle %}
....