qwc2/components/style/EditComboField.css

QGIS Web Client

div.edit-multi-select {
    border: 1px solid var(--border-color);
    padding: 0.25em;
    background-color: var(--input-bg-color);
    max-height: 5em;
    overflow-y: auto;
    text-align: left;
}

div.edit-multi-select label > input {
    margin-right: 0.25em;
}