[Malleys]

var obj2 = {
    'text.subText.value': 'value1',
    'text.modificator.name': 'name1',
    'text.modificator.params': 'params1',
    'attrs.title': 'title1'
};

function expand(object) {
    var result = {};

    for(var key in object) {
        var context = result;
        var keys = key.split(".");
        var property = keys.pop();

        context = keys.reduce((m,v) => {
            return v in m ? m[v] : m[v] = {};
        }, context);

        context[property] = object[key];
    }

    return result;
}

alert(JSON.stringify(expand(obj2), null, "\t"));