Simply generate the code and find the MDK driver file

Official Recommended Steps

                  ##### Data EEPROM Programming Function#####

===============================================================================

 [.] Any operation of erasing or programming should follow the following steps:
 (#) Call the @ref HAL_FLASHEx_DATAEEPROM_Unlock() function to enable data EEPROM access
     Erase control register access with Flash program.
 Call the required functions to erase or program data.
 (#) Call @ref HAL_FLASHEx_DATAEEPROM_Lock() to disable data EEPROM access
     Erase control register access with Flash programs (recommended)
     Protect DATA_EEPROM from possible accidental operations.

It only takes three steps to summarize the experiment.

1. Unlock
2. Write data (erase and write data but write 0x00)
3. Locking (it's recommended, but it's useless. It's not a big problem to use it.)

void Program_EEPROM(void)
{
    uint32_t data = 0x12345678;
  
    HAL_FLASHEx_DATAEEPROM_Unlock();

    HAL_FLASHEx_DATAEEPROM_Program( FLASH_TYPEPROGRAMDATA_WORD,  0x08080000,  data);
    HAL_FLASHEx_DATAEEPROM_Program( FLASH_TYPEPROGRAMDATA_WORD,  0x08080000 + 4,  data);
    
    HAL_FLASHEx_DATAEEPROM_Erase(FLASH_TYPEERASEDATA_WORD, 0x08080000);
    
    HAL_FLASHEx_DATAEEPROM_Lock();
}

• FLASH_TYPEPROGRAMDATA_WORD is a data type and can be Program word (32-bit) at a specified address OR Program word (16-bit) at a specified address OR Program word (8-bit) at a specified address.
• 0x08080000 is the address, which can be found in the official manual.
• Data is written data

Actual operation effect

Erase is also write

/**
  * @brief  Erase a word in data memory.
  * @param  Address specifies the address to be erased.
  * @param  TypeErase  Indicate the way to erase at a specified address.
  *         This parameter can be a value of @ref FLASH_Type_Program
  * @note   To correctly run this function, the @ref HAL_FLASHEx_DATAEEPROM_Unlock() function
  *         must be called before.
  *         Call the @ref HAL_FLASHEx_DATAEEPROM_Lock() to the data EEPROM access
  *         and Flash program erase control register access(recommended to protect 
  *         the DATA_EEPROM against possible unwanted operation).
  * @retval HAL_StatusTypeDef HAL Status
  */
HAL_StatusTypeDef HAL_FLASHEx_DATAEEPROM_Erase(uint32_t TypeErase, uint32_t Address)
{
  HAL_StatusTypeDef status = HAL_OK;
  
  /* Check the parameters */
  assert_param(IS_TYPEPROGRAMDATA(TypeErase));
  assert_param(IS_FLASH_DATA_ADDRESS(Address));
  
  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation(FLASH_TIMEOUT_VALUE);
  
  if(status == HAL_OK)
  {
    /* Clean the error context */
    pFlash.ErrorCode = HAL_FLASH_ERROR_NONE;

    if(TypeErase == FLASH_TYPEERASEDATA_WORD)
    {
      /* Write 00000000h to valid address in the data memory */
      *(__IO uint32_t *) Address = 0x00000000U;
    }

    if(TypeErase == FLASH_TYPEERASEDATA_HALFWORD)
    {
      /* Write 0000h to valid address in the data memory */
      *(__IO uint16_t *) Address = (uint16_t)0x0000;
    }

    if(TypeErase == FLASH_TYPEERASEDATA_BYTE)
    {
      /* Write 00h to valid address in the data memory */
      *(__IO uint8_t *) Address = (uint8_t)0x00;
    }

    status = FLASH_WaitForLastOperation(FLASH_TIMEOUT_VALUE);
  }
   
  /* Return the erase status */
  return status;
}  

If you don't understand it, you can search for pointers to force type conversion.

I have a couple of questions that I'm confused about.

• Does a new download erase this subregion?
• Can flash use the same function?