I have taken a "bad habit" by always using LBB to make my programs

But when it comes to a problem I can't solve by myself and need help that might come from the LB forum, I have to go "back" to LB.
I have made a program that will use multiple windows, 3 in all but for now, let's do it with 2.
I can make it work in LBB but not in LB....and I don't know how to do it in LB

Here is my extremely simplified code working in LBB. For now, it doesn't do anything else but opening the FIRST or the SECOND window at will.
NOMAINWIN
[FIRST]
WindowWidth = 400
WindowHeight = 200
UpperLeftX = int((DisplayWidth-WindowWidth)/2)
UpperLeftY = int((DisplayHeight-WindowHeight)/2)
MENU #FIRST,"Windows","First",[FIRST],"Second",[SECOND]
MENU #FIRST,"Exit","Exit",[QUIT.ALL]
STATICTEXT #FIRST, "FIRST WINDOW", 20, 10,200, 20
CLOSE #SECOND
OPEN "FIRST WINDOW" FOR window_nf AS #FIRST
#FIRST "TRAPCLOSE [QUIT.ALL]"
WAIT
[SECOND]
WindowWidth = 400
WindowHeight = 200
UpperLeftX = int((DisplayWidth-WindowWidth)/2)
UpperLeftY = int((DisplayHeight-WindowHeight)/2)
MENU #SECOND,"Windows","First",[FIRST],"Second",[SECOND]
MENU #SECOND,"Exit","Exit",[QUIT.ALL]
STATICTEXT #SECOND, "SECOND WINDOW", 20, 10,200, 20
CLOSE #FIRST
OPEN "SECOND WINDOW" FOR window_nf AS #SECOND
#SECOND "TRAPCLOSE [QUIT.ALL]"
WAIT
[QUIT.ALL]
CLOSE #SECOND
CLOSE #FIRST
END
This is the error message I get when using the same code in LB4.5.1 editor.
Can I make this work in LB4?