It looks like you've copied the relevant config line, and put Trickster in the wrong place in the copy. Instead, remove you copy-pasted line, and put "trickster" at the end of the "S:disableMobNames <" line, after the angle bracket. The angle brackets are most likely intended to enclose the names of all the mobs that you want to disable.This is my current openblocks.config file at the beginning. There is more to it but this is the pertinent part of it:
# Configuration file
additional {
# List any mob names you want disabled on the server
S:disableMobNames <
>
S:"disableMobNames Trickster" <
>
# Should player inventories be stored after death (can be later restored with ob_inventory command)
B:dumpDeadPlayersInventories=true
}
I am still getting tricksters to spawn.
Disclaimer: I have not messed with this feature, and as such I do not know the correct format. However, you'll probably need to use the mob's internal name... which I might be able to find or guess if I knew what mod these Tricksters are from.