- The three market Content Blocks preview as compact collapsible rows:

thumbnail of the actual image (hero background, intro image, insights
  cover), key copy in the summary line, full details expanded; card and
  intro-paragraph previews are wrapped in the same mechanism
- New SubmarketPluginPreview for vitec_usecaselist / vitec_productfeature /
  vitec_productlist: instead of bare standard boxes they now list the
  selected story titles (flagging stories that still lack a quote), the
  featured product and the hand-picked products in order
- Container-style collapse for whole page-module COLUMNS: a chevron at the
  right of every column header folds a section down to its title row,
  state kept per page and colPos in localStorage - the slot view of a
  sub-market page folds to six slim bands
- Previews sit under the page module's pointer-events lock and its
  click-to-edit layer: pointer events are re-enabled inside the collapse
  markup and the toggle runs on pointerdown in the capture phase
- Two more v14 removals fixed on the way, both latent in the OLDER preview
  classes too (Usecaseshow, Modelcard would have crashed the page module):
  GridColumnItem::getRecord() now returns a Domain\Record object, and
  StandaloneView is gone - previews normalize the record via a shared
  helper and render through the ViewFactory

packages/vitec/Resources/Public/Css/backend-preview.css

@@ -245,3 +245,86 @@
         display: none;
     }
 }
+
+/* =============================================================
+   Collapsible section previews (sub-market template, 2026-10-02)
+   Same practical effect as the container collapse on Two Columns,
+   built with <details> so it works for ANY element preview.
+   ============================================================= */
+details.vitec-collapse {
+    border-left: 4px solid #26358C;
+    background: var(--typo3-state-default-bg, #f8f9fa);
+    border-radius: 4px;
+}
+details.vitec-collapse > summary {
+    cursor: pointer;
+    padding: 0.6rem 0.75rem;
+    display: flex;
+    gap: 0.75rem;
+    align-items: center;
+    list-style: none;
+    font-size: 0.875rem;
+}
+details.vitec-collapse > summary::-webkit-details-marker { display: none; }
+details.vitec-collapse > summary::before {
+    content: '▸';
+    color: #F47937;
+    transition: transform 0.15s ease;
+    flex: 0 0 auto;
+}
+details.vitec-collapse[open] > summary::before { transform: rotate(90deg); }
+.vitec-collapse__label {
+    font-weight: 700;
+    color: #26358C;
+    white-space: nowrap;
+}
+.vitec-collapse__hint {
+    color: #666;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+}
+.vitec-collapse__thumb {
+    width: 72px;
+    height: 44px;
+    object-fit: cover;
+    border-radius: 3px;
+    flex: 0 0 auto;
+}
+.vitec-collapse__body {
+    padding: 0 0.75rem 0.75rem 2.1rem;
+    font-size: 0.875rem;
+}
+.vitec-collapse__body p { margin: 0.25rem 0; }
+.vitec-collapse__body img { max-width: 280px; border-radius: 3px; margin-top: 0.4rem; }
+
+/* The page module disables pointer events on preview content so clicks hit
+   the element row - re-enable them inside our collapsible previews, or the
+   summary can never be toggled (found 2026-10-02). */
+details.vitec-collapse,
+details.vitec-collapse * {
+    pointer-events: auto;
+}
+details.vitec-collapse > summary { user-select: none; }
+
+/* =============================================================
+   Collapsible page-module COLUMNS (sub-market sections etc.),
+   container-style: chevron button at the right of the column
+   header, state kept per page+column in localStorage.
+   ============================================================= */
+.t3-page-column-header { position: relative; }
+button.vitec-col-toggle {
+    position: absolute;
+    top: 50%;
+    right: 0.5rem;
+    transform: translateY(-50%);
+    border: 0;
+    background: transparent;
+    cursor: pointer;
+    font-size: 1rem;
+    line-height: 1;
+    color: #F47937;
+    padding: 0.25rem 0.4rem;
+}
+button.vitec-col-toggle:hover { color: #26358C; }
+td.t3-page-column.vitec-col-collapsed > :not(:first-child) { display: none; }