assets/css/src/task_list.css

.task-list-subtasks {
    display: table;
    width: 100%
}

@media (max-width: 768px) {
    .task-list-subtasks {
        display: block
    }
}

.task-list-subtask {
    display: table-row
}

@media (max-width: 768px) {
    .task-list-subtask {
        display: block
    }
}

@media (max-width: 768px) {
    .subtask-assignee,
    .subtask-time-tracking-cell {
        display: none
    }
}

.subtask-time-tracking {
    white-space: normal
}