HI. Is it possible to have a way where i can use all the gpio’s (except 3.3v 5v and com) as outputs to control relay boards.right now if i use add relay button, then i can only access certain gpios eg 5 6 12 13 16… i would like a setting where i can use the full gpio pins to control relays.
As far as I know- the 1Wire, SPI and I2C are hard-programmed, so they aren’t available. There IS an option in HTML Device Setup dashboard that asks if you want the I/O functions on or off- but I don’t believe it has any effect on the selection/inhibiting/allowing of GPIO ports.
You CAN use a MCP23008 GPIO port expander chip. This is supported in Cayenne. Using i2C or SPI bus, you can have as many GPIO ports as your heart desires. 
Right now some pins are reserved for special functions like 1 wire, SPI and I2C but you can use an expander like @HighTech mentioned. Unfortunately there is no way to use them but this has been requested in the past, so maybe some day