ShrinkVertically/Asset/css/shrink-vertically.css

/*
 * ShrinkVertically -- keep the board's horizontal scrollbar visible when columns
 * are vertically collapsed (gear menu "collapse vertically" / shortcut, which sets
 * localStorage vertical_scroll=0 and adds the class .board-task-list-compact).
 *
 * Kanboard core sets:  .board-task-list-compact { max-height: 90vh; }
 * That 90vh is measured from the top of the viewport and ignores the page header
 * above the board, so column + header together exceed the viewport and push the
 * horizontal scrollbar below the fold.
 *
 * We instead reserve a fixed pixel budget for the chrome above and below the task
 * list (page header + board column header + the horizontal scrollbar + a little
 * breathing room). A fixed-px budget is more reliable than a proportional vh value
 * because that chrome is a fixed height regardless of screen size.
 *
 * The pixel budget is the --sv-shrink-offset CSS variable. It is injected in the
 * page head from the plugin setting (Settings -> Shrink Vertically); when unset it
 * falls back to 240px below. Increase it if the scrollbar is still clipped, or
 * decrease it to make the columns taller.
 *
 * The selector is intentionally more specific than core's single-class rule, and
 * uses !important, so this override wins even alongside a theme (e.g. Essential).
 *
 * The min-height override is essential: Kanboard's drag-and-drop sets an INLINE
 * min-height on each column equal to its full content height
 * (BoardDragAndDrop.js: css("min-height", parent().height())). In CSS, min-height
 * beats max-height, so that inline value keeps tall columns from shrinking and our
 * max-height alone does nothing. A stylesheet !important overrides the inline
 * (non-important) min-height, so we reset it to 0 and let max-height win.
 */
#board td .board-task-list.board-task-list-compact {
    max-height: calc(100vh - var(--sv-shrink-offset, 240px)) !important;
    min-height: 0 !important;
}