It's actually a LOT more simple than the old way once you grasp it. But yes, there is a learning curve involved coming from the old way.
That example is simple, you just use mindrop and droplimit to force 1 item to drop every time (since probability was 100%) So:
lootdrop_entries 85, mindrop 1, droplimit 1, multiplier 1
lootdrop_entries 85 would have inside:
item1 10%
item2 10%
item3 10%
item4 10%
item5 10%
item6 10%
item7 10%
item8 10%
item9 10%
item0 10%
Since probability was 100%, none of the percentages will change of course. No more and no less than 1 of those 10 items will drop.
But changing it up, let's say the old probability was 80%. Then the same example would look like:
lootdrop_entries 85, mindrop 0, droplimit 1, multiplier 1
lootdrop_entries 85 would have inside:
item1 8%
item2 8%
item3 8%
item4 8%
item5 8%
item6 8%
item7 8%
item8 8%
item9 8%
item0 8%
Notice mindrop is now 0 because we are no longer guaranteed an item, and all the percentages dropped because multiplier is 20% lower. But, they all equal 80% - the old probability
Let's have some fun and show off what the new system can do.
Same example above, but:
mindrop 0, droplimit 0: 0 to all 10 of those items will drop.
mindrop 5, droplimit 0: 5-10 of those items will always drop.
mindrop 1, droplimit 2: 1-2 of those items will drop.
mindrop 0, droplimit 0 and all the items have a 50% chance of dropping: 0-10 items can drop, but most of the time 5 will (since "probability" is now 500%.)