I don't know if you still need this but here is something I made

on :text:!whitelist :#:{
if ($nick isop #) {
var %name $2
var %name2 $3
var %name3 $4
var %name4 $5
var %name5 $6
var %name6 $7
var %name7 $8
var %name8 $9
var %name9 $10
var %name10 $11
var %name11 $12
var %name12 $13
var %name13 $14
var %name14 $15
var %name15 $16
var %name16 $17
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name2
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name3
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name4
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name5
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name6
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name7
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name8
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name9
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name10
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name11
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name12
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name13
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name14
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name15
/write C:\Users\Lewis\Desktop\server\whitelist.txt %name16
}
}
it allows you to add up to 16 names at a time, where it says "C:\Users\Lewis\Desktop\server\whitelist.txt" you put the directory where your whitelist,txt is.

command usage example "!whitelist Sethbling Hypixel CaptinSparklez (up to 16 names)