How to make a column for a specific tag

You can add the column to a named column config:

INCIDENT_TABLE_COLUMN_LAYOUTS = {
    "mylayout": [
        ..
        IncidentTableColumn(
            "mytag",
            "MYTAG",
            "htmx/incidents/cells/_incident_tag.html",
            context={"tag": "MYTAG"},
        )
        ..
    ]
    ..
}