I find this solution that seem like work well. Sure is not best and elegant solution but i'm working with few data and i don't care too much to benchmark and i have only 2 days for develop calendar in custom cms. I stuck for a few hours on .refreshEvents() but seem like to work only with function or json but i can't manipulate data from db in the cms RESTAPI and i need to do in my browser JS.

This is my solution, declare and render calendar in function:

let calendarEl=[] // Global declaration
calendarOption={events: calendarEvent} // Calendar option

async function  createCalendar (){
      await $.get("/calendar/getAllEvents", function (response) {
            refreshEvents(response.data) // fnc manipulate response
          })
        // Declare calendar
        let calendar = new Calendar(calendarEl, calendarOption);
        calendar.destroy();
        calendar.render();
    }

In manipulation function i fetch the end point for update but if the calendarEvent.length>0 i set length of array to 0. This is the only solution that i find working. If you set calendarEvent=[] give me some issue and refresh not work.

function refreshEvents (data){
            //calendarEvent=[] This not work
            if(calendarEvent.length>0){
              // this work
              calendarEvent.length = 0
            }
            for (let i = 0; i < data.length; i++) {
                const el = data[i];
                // manipulate data
                event={
                    // create event object
                }
                // update global array
                calendarEvent.push(event)
            }
         }

In the end i call createCalendar() on startup and after insert/update/delete action

$(document).ready(async function () {      
      await createCalendar ()
      .
      .
}

Hope this is usefull for someone