Use SPIFFS like EEPROM

SPIFFShelper.h

struct spiffs_helper_t {
  
  File f;
  spiffs_helper_t(const char * _path ) {
    f = SPIFFS.open(_path, "r+"); // try to open if there... for read and write
    if (!f) {
      f = SPIFFS.open(_path, "w+"); // if fail open for read/write but new
    }
  };

  ~spiffs_helper_t() {
    f.close();  // close file when done
  }

  bool makesize(size_t size) {
    if ( size < f.size()) {
      return true;
    } else {
      f.seek(0, SeekEnd);

      do {
        f.write(0);
      } while (size > f.position() ) ;

      if (f.position() == size) {
        return true;
      } else {
        return false;
      }
    }

  }

  template <class T> int readfrom(int position, T& value)
  {
    if (!f) return 0;
    if (f.seek(sizeof(float)*position, SeekSet)) {

      byte* p = (byte*)(void*)&value;
      unsigned int i;
      for (i = 0; i < sizeof(value); i++)
        *p++ = f.read();
      return i;
    }
  }

  template <class T> int writeto(int position, const T& value)
  {
    if (!f) return 0;
    size_t location = sizeof(float) * position;
    bool success = false;
    if (!f.seek(location, SeekSet)) {
      if (makesize(location)) success = true;
    } else success = true;
    if (success) {
      const byte* p = (const byte*)(const void*)&value;
      unsigned int i;
      for (i = 0; i < sizeof(value); i++)
        f.write(*p++);
      return i;
    } else return 0;
  }

};