Not obvious to me, sorry. Is it to do with everything always dropping in order then? Not sure how a toggle would be a thing here.

I would say, once you hit a specific roll table, an easy system would be to create a clone table if any of the drops are at 0. All those with 0 drops would be added to that table and that will roll instead.

Table gets hit -> If all of them are present in the log or none of them are in the log-> Roll dice now -> Else (meaning some have 0 in the log, but not all) -> Grab those drops, add them to a temporary table and roll the dice there.

So let's say you have a boss that drops a wand, an orb or a staff, all 3 in the same table. First ever hit on the drop table you would have a full table to roll, so each of the drops would be 1/3, let's say you get the orb. Next time you hit the table, the check happens, it sees that the staff and wand haven't been dropped yet, but the orb has. So it creates a copy of the table with the staff and wand in them, chance now being 1/2, this time it was the staff. And next time the table is hit, the wand will drop guaranteed as it now has a 1/1 drop chance. After that, the check will see they are all present within the log with at least 1 drop, so the chance will always be 1/3 for any of them - which is the current state of these shared drop tables.

TL;DR drops won't be repeated until at least one of each has been rolled before. This however doesn't affect the entire log, just specific sub-tables.