Make sure that setting is valid for the Minecraft version you're using - it's possible that either you're on a version of Paper from before it was added, or they've since removed it.
#Missing Setting in Paper Servers
plucky turret
Ok Ty
gaunt copper
Bisect pulls the latest version when you restart.
On their wiki, it says that setting specifically "may be removed at any time."
And it looks like as of 2 weeks ago, it isn't working properly anyway.
Since it's unsupported, you may have to add the key and value both to the file.
That means you have to add the whole line to the file.
¯_(ツ)_/¯
Nothing Bisect does would prevent this from working, and it sounds like the feature is bugged anyway.