iview have answered similar questions on github. After the tree component uses the render function, it thinks that all the logic and effects need to be written manually. The tree component only provides the simplest data presentation effect. If you want to click on the background, you can register a click event implementation in the render function

my method should be more reliable.
html sets ref= "tree"

<Tree :data="treeData" ref="tree" :render="renderContent"></Tree>

js method

renderContent(h, { root, node, data }){
    return h('span',{
        style:{
            color:'-sharp666',
            cursor:'pointer'
        },
        domProps:{
            className:'btn'
        },
        on:{
            click:(e)=>{
                let btns=this.$refs.tree.$el.querySelectorAll('.btn')
                for(let i=0;i<btns.length;iPP){
                    btns[i].style.backgroundColor='-sharpfff'
                }
                e.path[0].style.backgroundColor="-sharp2d8cf0";//
            }
        }
    },data.title)
}