Dark theme for the VSCode Kanba extension (https://github.com/mkloubert/vscode-kanban). Screenshot in comments. The commandbar.json can be used with the vscode-commandbar extension (https://github.com/ppatotski/vscode-commandbar) to add a shortcut for the Kanban board to the status bar.

commandbar.json

{
  "skipTerminateQuickPick": true,
  "skipSwitchToOutput": false,
  "skipErrorMessage": true,
  "commands": [
    {
      "text": "$(project) Kanban",
      "tooltip": "Open Kanban Board",
      "color": "white",
      "command": "extension.kanban.openBoard",
      "commandType": "palette",
      "alignment": "left",
      "skipTerminateQuickPick": false,
      "priority": 0
    }
  ]
}

vscode-kanban.css

body {
    background-color: inherit;
}

.border-dark {
    border-color: transparent !important;
}

.border {
    border: none !important;
}

.text-dark {
    color: #e0e0e0 !important;
}

.text-white {
    color: #e0e0e0 !important;
}

.bg-light {
    background-color: transparent !important;
}

.modal-header .bg-secondary {
    background-color: #272727 !important;
}

.card {
    position: relative;
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-orient: vertical;
    -webkit-box-direction: normal;
    -ms-flex-direction: column;
    flex-direction: column;
    min-width: 0;
    word-wrap: break-word;
    background-color: transparent !important;
    background-clip: border-box;
    border: none;
    border-radius: 0;
}

.card-header {
    background-color: #ffffff27 !important;
    border-radius: 6px;
    padding: 6px !important;
    justify-content: center;
    border-left: 5px solid #ffffff5b;
}

.card-header span {
    display: inline-block;
    height: 100%;
    margin-left: 1em;
    margin-top: 3px;
}

.card-body {
    -webkit-box-flex: 1;
    -ms-flex: 1 1 auto;
    flex: 1 1 auto;
    padding: 0 !important;
    padding-top: 6px !important;
}

body main .row .col {
    padding-bottom: 10px;
    padding-left: 8px;
    padding-right: 8px;
}

.bg-primary .card-header {
    border-left: 5px solid var(--primary) !important;
}

.bg-warning .card-header {
    border-left: 5px solid var(--warning) !important;
}

.bg-success .card-header {
    border-left: 5px solid var(--success) !important;
}

.vsckb-kanban-card {
    clear: both;
    display: table;
    margin-bottom: 8px;
    width: 100%;
    border-radius: 5px;
    overflow: hidden;
    background-color: rgba(255, 255, 255, 0.13) !important;
}

.vsckb-kanban-card .vsckb-kanban-card-info .vsckb-kanban-card-body {
    margin-top: 0;
    min-height: 0;
    overflow-x: hidden;
    padding: 2px 8px;
    word-wrap: break-word;
}

.vsckb-kanban-card .bg-white {
    background-color: transparent !important;
}

.vsckb-kanban-card .bg-info {
    background-color: rgba(255,255,255,0.2) !important;
}

.vsckb-kanban-card .bg-dark {
    background-color: var(--warning) !important;
}

.vsckb-kanban-card .vsckb-kanban-card-info .vsckb-kanban-card-category {
    clear: both;
    margin-left: 0.5em;
    display: block;
    width: min-content;
    font-size: 0.75em;
    font-style: normal;
    padding: 0 6px 2px 6px;
    border-radius: 4px;
    background-color: rgba(255,255,255,0.2);
}

.vsckb-kanban-card .vsckb-kanban-card-info .vsckb-kanban-card-progress {
    clear: both;
    display: block;
    height: auto !important;
    overflow: hidden;
    padding: 0;
    width: 100%;
    margin: 5px 0;
    background-color: rgba(255,255,255,0.1);
}

.vsckb-kanban-card .vsckb-kanban-card-info .vsckb-kanban-card-progress .bg-danger {
    background-color: var(--primary) !important;
}

#vsckb-card-done .vsckb-kanban-card .bg-info, #vsckb-card-done .vsckb-kanban-card .bg-dark, #vsckb-card-done .vsckb-kanban-card .bg-danger {
    background-color: var(--success) !important;
}