Suppose you have these Dropdowns with Arrows, you want to change these to custom icon.
Use this to Custom CSS
/* Filter Arrow */
.custom-filter-container .sortDropdown.sqs-block-archive .icn-down-open:before, .custom-filter-container .filterDropdown.sqs-block-archive .icn-down-open:before {
content: url(https://api.iconify.design/teenyicons/down-small-solid.svg) !important;
font-family: initial !important;
}
.custom-filter-container .filterDropdown.sqs-block-archive .archive-dropdown-toggle-checkbox:checked~.archive-dropdown-toggle-label .icn-down-open:before, .custom-filter-container .sortDropdown.sqs-block-archive .archive-dropdown-toggle-checkbox:checked~.archive-dropdown-toggle-label .icn-down-open:before {
content: url(https://api.iconify.design/teenyicons/up-small-solid.svg) !important;
font-family: initial !important;
}
Result
Remember to replace example icon url in the code