Arduino Nano IoT 33 Char Array size constraints
You can use the flash memory of the SAMD21 MCU used on Nano 33 IoT, if you don't write to often. Flash memories have limited count of write-erase cycles. It is guarantied for 10000 writes.

For Arduino SAMD boards like the nano 33 IoT you can use the FlashStorage library. The library is in Library Manager.