@@ -0,0 +1 @@
+- Allow configuration of horizontal legend max height [[#7359](https://.com/plotly/plotly.js/pull/7359)]

@@ -33,6 +33,18 @@ module.exports = {
 editType: 'legend',
 description: 'Sets the color of the border enclosing the legend.'
 },
+maxheight: {
+valType: 'number',
+min: 0,
+editType: 'legend',
+description: [
+'Sets the max height (in px) of the legend, or max height ratio (reference height * ratio) if less than one.',
+'Default value is: 0.5 for horizontal legends; 1 for vertical legends. The minimum allowed height is 30px.',
+'For a ratio of 0.5, the legend will take up to 50% of the reference height before displaying a scrollbar.',
+'The reference height is the full layout height except for vertically oriented legends with',
+'a `yref` of `"paper"`, where the reference height is the plot height.'
+].join(' ')
+},
 borderwidth: {
 valType: 'number',
 min: 0,

@@ -188,6 +188,7 @@ function groupDefaults(legendId, layoutIn, layoutOut, fullData) {
 
 coerce('xanchor', defaultXAnchor);
 coerce('yanchor', defaultYAnchor);
+coerce('maxheight', isHorizontal ? 0.5 : 1);
 coerce('valign');
 Lib.noneOrAll(containerIn, containerOut, ['x', 'y']);
 

@@ -3442,6 +3442,12 @@
 "min": 30,
 "valType": "number"
 },
+"maxheight": {
+"description": "Sets the max height (in px) of the legend, or max height ratio (reference height * ratio) if less than one. Default value is: 0.5 for horizontal legends; 1 for vertical legends. The minimum allowed height is 30px. For a ratio of 0.5, the legend will take up to 50% of the reference height before displaying a scrollbar. The reference height is the full layout height except for vertically oriented legends with a `yref` of `\"paper\"`, where the reference height is the plot height.",
+"editType": "legend",
+"min": 0,
+"valType": "number"
+},
 "orientation": {
 "description": "Sets the orientation of the legend.",
 "dflt": "v",