This actually isn’t MineOS related, it is Spigot/Paper related as they had added a restart command sometime back (well as far back as I can remember it’s always been there). Upon using this restart command in-game, the server would react the same way it does when you use the stop command, except at the very end it calls/launches/runs a script, typically named restart.sh that can be created and placed within the server’s main/base directory, which then executes a series of commands, depending upon what commands you put inside the script file.
My guess here is that this typically doesn’t play well with MineOS because MineOS launches servers differently. However I’ve seen time and time again that you can trigger/interact with the web ui button commands using it’s back-end script being that the ui is just a front-end which triggers actions and commands via the back-end. So, in order for the restart script to work and function properly with MineOS chances are that script would have to either launch your Minecraft server in the same way that MineOS does, or that script would just have to interact with MineOS’ back-end which will tell MineOS to start the server the same way it would have if you clicked start or had it start on boot. How to go about doing so you ask? I currently have no idea despite the fact that I’ve seen it over and over. But interacting with MineOS’ back-end would be the best way to go about this in my opinion.
Edit: Categorized under Command Line
Edit #2:
Namely: