Yes, you can store whatever you like in Flash, by using IAP (read the User Manual to find how to program the flash in your code, using IAP).
The problem is that flash has a minimum program size (page) which is typically 256 bytes or more, so to change just 6 bytes, you would need to read an entire page into RAM, erase the page, change the bytes in the RAM copy, and then write RAM copy back into flash. Alternatively, you could just reserve a whole page (preferably at or near the top of flash) and overwrite the whole page.
There are many questions (and answers) on this forum about the subject of emulating eprom in flash