Sensecap S2120 update time shorter than 5 minutes

I have a weather station S2120 which works very well with TTS using Datacake.
During initial set-up of S2120 (6 months ago), the minimum update time was then 5 minutes.
Now I found in the manual chapter 11. Lorawan Downlink Command, that it’s possible to change the uplink interval to 1 minute.
It doesn’t work for me, I do something wrong I’m sure.
Can you please tell me step by step, word by word, this procedure how to set up this Payload formatters downlink command in Custom Javascript.