Interesting, so it should and does have that feature, just for some reason it's not functional for making G code files for the i3 Mega (newb who just got an Anycubic i3 Mega Ultra base yesterday and have been trying to get Cura to work nicely right from the get go). But for me, going by settings -> profile -> manage profile -> material doesn't work, it sticks to using what ever Cura is defaulting to for this printer. I can also hit the custom tab, and even make changes to temperatures there and it still produces G code that does not pay attention to user set temperature settings (haven't played around with other settings - yet). The only solution I have at the moment is to use notepad and manually edit the resulting G code file to fix bed/extruder temperatures (M104/M109, M140/M190).