Cant copy and paste a part with script and still work?

If you want to clone the window or any other object/instance use the :Clone() function!

--How to clone parts!

local GlassWindow1 = game.Workspace.GlassWindow1
GlassWindow1.Transparency = 0.7 
GlassWindow1.Material = ("Glass")

--If you want to clone this window use the :Clone() function!

local glasswindowClone = GlassWindow1:Clone()
--You can also clone it like this: game.Workspace.GlassWindow1:Clone()

--When you make a new clone it does not "spawn" inside the Workspace.
--You will need to put it inside the Workspace by Parenting it to the Workspace.

glasswindowClone.Parent = workspace

--Boom! You have a copy of the window!
--If you want to continuously spawn/clone them you can use a loop.

--I am assuming you do not know how a loop works yet, and I do not want this to become too confusing!
--If you would like to learn more about scripting I would recommend watching Alvin Blox's 2019 - 2020 Beginner Scripting Series on Youtube!

while true do

    local glasswindowClone = GlassWindow1:Clone()

    --Before putting the window clone in the Workspace you can set its properties such as it name, transparency, etc.
    glasswindowClone.Name = "WindowClone"

    glasswindowClone.Parent = workspace

    --Waits 1/10th of a second before proceeding.
    wait(0.1)
end