Edit File(JSON) on SD Card

I am currently working on an ESP32 Project, where I want to save some sensor data in a JSON File.
I have to add the new sensor data in the middle of the JSON File. Is there a better way than copying everything before and after the spot, where I want to add something and create a new file, where I paste the first part, add the new part and then paste the last part?

How many bytes is the JSON file at max ?

UKHeliBob:
How many bytes is the JSON file at max ?

I don't have a number, but I think it could get quite large, because I have a few Timevalues in Unixtime in there. But i think, it'll stay small enough to store the content in a String.

How about seeking to the insertion point, reading the rest of the file into an array (not a String), seeking back to the insertion point, writing the new data to the file then writing the data previously saved in the array

NOTE : I have not tried this and, of course, it depends on memory being available