Would be nice if inline CSS worked for trees as well as for DataTables. Right now it’s rendered as webix_tree_item [object Object]:
Behavior will be normalized in Webix 2.2. All data components will support object notation for $css property.
By the way, in above snippet you are using “css” property defined as part of configuration ( it is applied to one column, not to the data record )
In case of tree you can define “css” in configuration as well ( it will be applied to the whole tree )