Is there any way to run the /execute as run command in Minecraft with a non built-in command?
Solution 1:
This has been reported as something which will not by patched by spigot head developer. https://hub.spigotmc.org/jira/browse/SPIGOT-4327
luckily, the following tool exists: https://github.com/JorelAli/1.13-Command-API