una/studio/template/css/options.css

div.bx-stg-cells {
    position: relative;
    display: flex;
}
div.bx-stg-cells div.bx-sc-cell {
    position: relative;
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;
    flex: 1 1 auto;
}
div.bx-stg-cells div.bx-sc-cell .bx-btn {
    margin: 0.25rem;
    white-space: nowrap;
}

/*-- Manage --*/
div.bx-stg-manage div.bx-sc-cell.bx-sc-right {
    margin: -0.25rem;
    justify-content: flex-end;
}

/*-- Mixes --*/
div.bx-stg-mixes div.bx-sc-cell.bx-sc-select {
    width: 50%;
}
div.bx-stg-mixes div.bx-sc-cell.bx-sc-new {
    width: 50%;

    margin: -0.25rem;
    justify-content: flex-end;
}
div.bx-stg-mixes div.bx-sc-cell select {
    width: auto;
}