Sorry, that's a "Premium" feature. In all seriousness, my XSE Premium has a dedicated button to switch to 360/front camera. I don't recall if it lets you check the rear cam as I don't use it that often. It's annoying that modern cars have several cameras but they can't be used on-demand to help with visibility or as dashcams.
Dang. I'm hoping against hope that some fanatic has found/will find the magic pushbutton sequence, inCANtation, or engineer a hack to do it. In the meantime I left my humble request for product improvement with Toyota at: Toyota Customer Service
Only in R. If you get the top trim with the Advanced Tech Package, you can activate the 360 cameras if you're at low speed, but there's no way to do anything if you're at normal driving speeds. (at least for US cars - I can't be 100% certain the same is true for EU/JDM models)
The last time I looked into this with my Gen 3, it required installing a pulse generator to "fool" the system into thinking the car was in motion. I can't imagine it's any easier in my Gen 5.
