Keyed access in PIC config settings for the WWDT
It appears that Microchip data sheet 40001843D mentions "keyed access" for bits in the WDTCON1 register in error. Access to these bits are read-only when CONFIG3 bits WDTCWS are not 111. When they are 111 the WDTCON1 can be written at any time.

The term "keyed access" usually means executing a specific sequence of instructions to enable write access to bits in a Special Function Register. See section: 11.1.2 NVM Unlock Sequence for an example of how this works for writing to program flash or EEPROM memory.