I haven't messed much with the addon, but in this particular area, local variables get cleared.
I tried to do a local variable list, to add the items into a list, but would always get cleared after the loop finished.
I resorted to using a RAM variable, but in this case, you can see what all is happening in the ss
Example
on mythicmob deathevent:
set {_uuid} to uuid of activemob event-activemob
broadcast "UUID - Before: %{_uuid}%"
loop all items of mobdrop event-mobdrop:
set {_test} to (loop-mobitem).getItem()
add {_test} to {-drops::%{_uuid}%::*}
broadcast "UUID - Loop: %{_uuid}%"
remove mobitem loop-mobitem from mobdrop event-mobdrop
broadcast "UUID - After: %{_uuid}%"
set {_uuid} to uuid of activemob event-activemob
broadcast "UUID - Reset: %{_uuid}%"

I haven't messed much with the addon, but in this particular area, local variables get cleared.
I tried to do a local variable list, to add the items into a list, but would always get cleared after the loop finished.
I resorted to using a RAM variable, but in this case, you can see what all is happening in the ss
Example