update

dist/bundle.css

@@ -4665,6 +4665,9 @@ ul.ztree.zTreeDragUL {
 .bi-multidate-segment .bi-multidate-editor {
   font-size: 14px;
 }
+.bi-multilayer-select-level-tree .tree-view {
+  min-width: 100%;
+}
 .bi-multilayer-single-level-tree .tree-view {
   min-width: 100%;
 }

dist/bundle.js

@@ -94236,7 +94236,7 @@ BI.MultiLayerSelectLevelTree = BI.inherit(BI.Widget, {
         this._assertId(nodes);
         this.tree = BI.createWidget({
             type: "bi.custom_tree",
-            element: this,
+            cls: "tree-view display-inline",
             expander: {
                 type: "bi.select_tree_expander",
                 isDefaultInit: o.isDefaultInit,
@@ -94264,6 +94264,13 @@ BI.MultiLayerSelectLevelTree = BI.inherit(BI.Widget, {
                 self.fireEvent(BI.MultiLayerSelectLevelTree.EVENT_CHANGE, arguments);
             }
         });
+
+        BI.createWidget({
+            type: "bi.adaptive",
+            element: this,
+            scrollable: true,
+            items: [this.tree]
+        })
     },
 
     populate: function (nodes) {

dist/fineui.css

@@ -4665,6 +4665,9 @@ ul.ztree.zTreeDragUL {
 .bi-multidate-segment .bi-multidate-editor {
   font-size: 14px;
 }
+.bi-multilayer-select-level-tree .tree-view {
+  min-width: 100%;
+}
 .bi-multilayer-single-level-tree .tree-view {
   min-width: 100%;
 }

dist/widget.css

@@ -189,6 +189,9 @@
 .bi-multidate-segment .bi-multidate-editor {
   font-size: 14px;
 }
+.bi-multilayer-select-level-tree .tree-view {
+  min-width: 100%;
+}
 .bi-multilayer-single-level-tree .tree-view {
   min-width: 100%;
 }

dist/widget.js

@@ -7756,7 +7756,7 @@ BI.MultiLayerSelectLevelTree = BI.inherit(BI.Widget, {
         this._assertId(nodes);
         this.tree = BI.createWidget({
             type: "bi.custom_tree",
-            element: this,
+            cls: "tree-view display-inline",
             expander: {
                 type: "bi.select_tree_expander",
                 isDefaultInit: o.isDefaultInit,
@@ -7784,6 +7784,13 @@ BI.MultiLayerSelectLevelTree = BI.inherit(BI.Widget, {
                 self.fireEvent(BI.MultiLayerSelectLevelTree.EVENT_CHANGE, arguments);
             }
         });
+
+        BI.createWidget({
+            type: "bi.adaptive",
+            element: this,
+            scrollable: true,
+            items: [this.tree]
+        })
     },
 
     populate: function (nodes) {

src/css/widget/multilayerselecttree/multilayerselecttree.css

@@ -0,0 +1,3 @@
+.bi-multilayer-select-level-tree .tree-view {
+  min-width: 100%;
+}

src/less/widget/multilayerselecttree/multilayerselecttree.leveltree.less

@@ -0,0 +1,5 @@
+.bi-multilayer-select-level-tree {
+  .tree-view {
+    min-width: 100%;
+  }
+}

src/widget/multilayerselecttree/multilayerselecttree.leveltree.js

@@ -71,7 +71,7 @@ BI.MultiLayerSelectLevelTree = BI.inherit(BI.Widget, {
         this._assertId(nodes);
         this.tree = BI.createWidget({
             type: "bi.custom_tree",
-            element: this,
+            cls: "tree-view display-inline",
             expander: {
                 type: "bi.select_tree_expander",
                 isDefaultInit: o.isDefaultInit,
@@ -99,6 +99,13 @@ BI.MultiLayerSelectLevelTree = BI.inherit(BI.Widget, {
                 self.fireEvent(BI.MultiLayerSelectLevelTree.EVENT_CHANGE, arguments);
             }
         });
+
+        BI.createWidget({
+            type: "bi.adaptive",
+            element: this,
+            scrollable: true,
+            items: [this.tree]
+        })
     },
 
     populate: function (nodes) {