discourse/app/assets/stylesheets/common/select-kit/multi-select.scss

.select-kit {
  &.multi-select {
    width: 300px;
    background: var(--secondary);

    .select-kit-filter {
      & + .selected-content,
      & + .select-kit-collection {
        border-top: 1px solid var(--primary-low);
      }
    }

    .select-kit-row {
      min-height: 1px;
    }

    &.is-disabled {
      .multi-select-header {
        background: var(--primary-low);
        border-color: var(--primary-low-mid);
        color: var(--primary-medium);
        .d-icon {
          color: var(--primary-medium);
        }
      }
    }

    .selected-content {
      display: flex;
      width: 100%;
      flex-wrap: wrap;
      padding: 0;
      justify-content: flex-start;
      box-sizing: border-box;
      border-bottom: 1px solid var(--primary-low);
      padding: 0.25em 0.25em 0 0.25em;

      .selected-choice {
        margin: 0 0.25em 0.25em 0;
        font-size: var(--font-down-1);

        &.selected-choice-color {
          border-bottom: 2px solid transparent;
        }
      }
    }

    .multi-select-header {
      background: var(--secondary);
      border-color: var(--primary-medium);

      .formatted-selection {
        margin: 0;
        cursor: pointer;
        @include ellipsis;
        display: inline-block;
      }

      .select-kit-header--filter {
        display: flex;
        flex-wrap: wrap;
        margin: -0.35em;
        margin-left: -0.25em;
        position: relative;
        .selected-choice {
          margin: 0.125em 0.25em 0.125em 0;
          padding: 0.2em 0.3em;
          font-size: var(--font-down-1);

          &.selected-choice-color {
            border-bottom: 2px solid transparent;
          }
        }

        .select-kit-filter {
          display: inline-flex;
          flex: 1 1 30px;
          width: auto;
          margin-left: 0.25em;
          position: static;
          min-height: 28px;
          &.is-expanded {
            padding: 0;
          }
          .filter-input {
            min-height: auto;
          }
        }
      }
    }

    &.is-expanded .multi-select-header,
    .multi-select-header:focus {
      @include default-focus;
    }
  }
}