The bottom line is this: I have a plugin that allows you to enter commands without ' / ' also there is a plugin which has a command to open a virtual chest, when the player enter the command without '/' chest opens, but its keyboard does not disappear. If you enter the command with a '/', closes the chat and removes the keyboard, everything is fine. Is it possible to fix this?
I won't agree with or disagree with your point, but I'd like to point out that "no API" never implies "not possible".