User:MonkeysHK/sandbox9

 .dual-table { display: flex; flex-direction: row; margin: 12px 0; } .dual-table + .dual-table { margin-top: -12px; } .dual-table table { margin: 0; height: unset !important; flex-grow: 1; justify-content: stretch; align-content: stretch; } .dual-table .seperator-cell { border-bottom: 5px solid var(--theme-accent-color); } @media screen and (max-width: 800px) { .dual-table { flex-direction: column; } }

Structure:

Suggestions:
 * Make a template creating a dual table: