currently I use nrf_gpio_pins_set() and and nrf_gpio_pins_clear() from nrf_gpio.h to set and clear specific GPIO ports, respectively. If I want to change the current state of -say- 4 GPIO ports at once (some of them may be cleared, some of them may be set), how do I do that? It would be important that the change on all pins happens at the same time.
Read the GPIO port to get the current state, set and clear bits in that value, then write it back.
Just as there is a GPIO->OUTSET and a GPIO->OUTCLR register, so there is a GPIO->OUT register you can write to set the whole register at once.