If there are no established standards for notating music with multiple tempos here are some suggestions.
Galley view could group staves according to which tempo they were aligned with. But how is music with multiple tempos scored in Page view? I presume that if a score divides pages according to time periods instead of bar lengths - with staves showing as various widths on each page - that this won’t work because it won’t be possible to align sounds vertically - and therefore the pages for each tempo would work better if shown left to right - side by side - with highlighting showing where each page is up to - and each page turning when it needs to. A double, triple or quadruple page spread - or whatever. The conductor could use either a desktop computer running a big screen or screens to oversee the work (the conductor is only there for reasons of musicality - not tempo). And perhaps he or she could switch between the click tracks for each required tempo if he or she wished. Or if he or she wishes to hear them all at once - the click tracks could have different pitches and sounds to help him or her tune in on one.
I hope that even if this kind of functionality doesn’t exist in an app any time soon that my ponderings in some way suggest ways that developers can design more pressing features now in a way that leaves the door open for less pressing additions.