Understand, and you are right.
When working with formulas such as
=EPMMEMBER([KEY_FIGURE].[].[CONSENSUSDEMAND])
I could not manage either, as I did not find any possibility to add time information.
But if you put in formula such as =J5+K6 it does work
Surely disadvantage is that you shall not change the order of the key figures as the system is stupid and would mess up.
Plus, you need to catch in the formula for the first period that the previous period does not have a value but text e.g. by something like this:
IF(IFERROR(INT(zelle)); calculation 1 ; calculation 2)
Plus you can check if the kf is the right one by e.g.
=IF((ISNUMBER(SEARCH("Global Demand Planning Quantity Prev Cycle";$P6))); calculation 1; calculation 2)
$P6 would be the cell to check the kf name and with the dollar you make sure that alwyas the same column is checked and only the row is moved.
But in general for those kind of calculation my recommendation would be to tell the users for not changing the order of KF .
Alternatively you can write VBA macro for that, but that would be possible for real storage keyfigures that have editability.