Node-Red how to group data in an object and then send to payload

I need help with grouping variables.
I have an object called box 1 , I would like to write values into it ( the number of values can change)
When the next object named box 2 comes I finish writing to box 1 and write to box 2.
The box 1 object is sent to msg.payload.
And so the next.

I have something like this, but no idea how to do a loop of unknown number of values.

[{"id":"6c21c63f.45b098","type":"tab","label":"Flow 1","disabled":false,"info":""},{"id":"cc13338b.ba10d","type":"function","z":"6c21c63f.45b098", "name": "Update Array", "func": "let pay = msg.payload ;arr = flow.get(elements)|| [];};Position is the index of element in the array/// If element is not in the table it will be added to the end { arr.indexOf(pay);}.push(pay)} else { arr.splice(pos, 1);}nflow.set(elements,arr);\nmsg.payload = [....arr];\nreturn msg;\n","outputs":1,"noerr":0,"initialize":"","finalize":"","x":430,"y":300,"wires":[["cd124bf7.2e0238"]]},{"id":"cd124bf7.2e0238","type":"debug","z":"6c21c63f.45b098","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":610,"y":300,"wires":[]},{"id":"7f568e1d.58c21","type":"inject","z":"6c21c63f.45b098","name":"","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"One","payloadType":"str","x":190,"y":220,"wires":[["cc13338b.ba10d"]]},{"id":"7145ffa.f20ff","type":"inject","z":"6c21c63f.45b098","name":"","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"Two","payloadType":"str","x":190,"y":260,"wires":[["cc13338b.ba10d"]]},{"id":"f038b7d6.8279f8","type":"inject","z":"6c21c63f.45b098","name":"","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"Three","payloadType":"str","x":190,"y":300,"wires":[["cc13338b.ba10d"]]},{"id":"48446f7f.89b58","type":"inject","z":"6c21c63f.45b098","name":"","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"Four","payloadType":"str","x":190,"y":340,"wires":[["cc13338b.ba10d"]]},{"id":"41b04df4.57e294","type":"inject","z":"6c21c63f.45b098","name":"","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"Five","payloadType":"str","x":190,"y":380,"wires":[["cc13338b.ba10d"]]},{"id":"c5854399.1d46b","type":"inject","z":"6c21c63f.45b098","name":"","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"Six","payloadType":"str","x":190,"y":420,"wires":[["cc13338b.ba10d"]]},{"id":"f97e5bae.602af8","type":"inject","z":"6c21c63f.45b098","name":"","repeat":"","crontab":"","once":true,"onceDelay":0.1,"topic":"","payload":"Start","payloadType":"str","x":190,"y":140,"wires":[["90ad31e5.3a953"]]},{"id":"90ad31e5.3a953","type":"change","z":"6c21c63f.45b098","name":"Empty array","rules":[{"t":"set","p":"elements","pt":"flow","to":"[]","tot":"json"}],"action":"","property":"","from":"","to":"","reg":false,"x":390,"y":140,"wires":[[]]}]

The flow you pasted does something completely different.
When a value arrives the first time it is added to the array, and when it arrives the second time it is removed from it.
As I understand it, you are talking about something else. It has to write to the array until another message arrives. The question is what exactly is the difference?

Hello
The 1 number is the rack number, then the elements are put into the rack.
When the rack is full it leaves and a new one comes with a new number and we put the elements in it.
I have no idea how to send the set to payload after each rack change.

Can you give an example of the data that comes in on the payload.
Is the payload as in the example a single string data type or perhaps an array or object?
How can you distinguish a new rack and when it is full?