Thank you for your rating!
In the future, please use the Discord channel (
https://customitems.page.link/discord) for support. But, anyways, to silence command output when running the /cui drop command, you can use the new [silent] argument in 4.0.16
Added new "silent" option in /cui drop command:
/cui drop <item> <world> <x> <y> <z> [amount] [naturally] [silent]
For your example, this will drop the item silently
/cui drop coal Main -31 75 -69 1 true true