Is this circuit design for multi-function button box good?
No, if &quot;select&quot; switch is ON, any &quot;function&quot; switch will short all the power line behind 10K via 2 diodes to the ground, so the second.....third.... functional buttons will not work this time (during pressing one)
GPIO inputs should be programmed with pull-up resistors ON
Some example to fix:

Couple thoughts:

All diodes looks could be safely excluded (shorted).
All transistors could be, for example, n-p-n - and connected the same way - left and right side, do not see the reason to use different (PNP)