In short, can I, and how do I, assign other pins for SPI?
I think not,
and much more to the point would be your explanation as to why you would want to do that.
SS is not part of the ISP bus.
Some devices have software SPI , but that doesn't mean you get to change Arduino's hardware SPI.
It is also sometimes referred to as Chip Select or CS.
What is SS then? The graphic in the initial post labels it something to do with SPI.
SS does not have to be used as a chip select driver, but it has to be an output.
I can do the something else on other pins
That sounds like a really good idea.
/* Create instance of library used to communicate with the OLED. *//* This configuration for remoteWeatherStation-PRX */U8G2_SSD1325_NHD_128X64_1_4W_SW_SPI u8g2( /* rotation zero */ U8G2_R0, /* clock=*/ 7, /* data=*/ 6, /* cs=*/ 5, /* dc=*/ 4, /* reset=*/ 3);
You can see that I have assigned pins (other that 9-13) to those nice SPI tasks. This works! Clock, data, cs and dc are working from pins other that the Arduino standard pins!How does that happen?