Modify the server properties file the way you want to, and save. Then, right click on the file from the manager and hit “import server properties.” Done.
Go into configuration for the instance, and select “Minecraft.” In that area, you can modify the various values that are actually present in the server.properties file.
The first option doesn’t work in this context. I’m waiting on an answer to my question, as those are the only valid reason why a user would need to alter that setting.