Question: Is there a way to force shift lock in a script?

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#22 
game.Workspace.CurrentCamera.CameraType = "Fixed"
#23

There is some code on the website Customizing the Camera | Roblox Creator Documentation

local Players = game:GetService("Players")
local ContextActionService = game:GetService("ContextActionService")
local UserInputService = game:GetService("UserInputService")
local RunService = game:GetService("RunService")
 
local camera = workspace.CurrentCamera
local cameraOffset = Vector3.new(2, 2, 8)
local player = Players.LocalPlayer
 
player.CharacterAdded:Connect(function(character)
 
	local humanoid = character:WaitForChild("Humanoid")
	local rootPart = character:WaitForChild("HumanoidRootPart")
	humanoid.AutoRotate = false
 
	local cameraAngleX = 0
	local cameraAngleY = 0
 
	local function playerInput(actionName, inputState, inputObject)
		-- Calculate camera/player rotation on input change
		if inputState == Enum.UserInputState.Change then
			cameraAngleX = cameraAngleX - inputObject.Delta.X
			-- Reduce vertical mouse/touch sensitivity and clamp vertical axis
			cameraAngleY = math.clamp(cameraAngleY-inputObject.Delta.Y*0.4, -75, 75)
			-- Rotate root part CFrame by X delta
			rootPart.CFrame = rootPart.CFrame * CFrame.Angles(0, math.rad(-inputObject.Delta.X), 0)
		end
	end
	ContextActionService:BindAction("PlayerInput", playerInput, false, Enum.UserInputType.MouseMovement, Enum.UserInputType.Touch)
 
	RunService.RenderStepped:Connect(function()
		if camera.CameraType ~= Enum.CameraType.Scriptable then
			camera.CameraType = Enum.CameraType.Scriptable
		end
		local startCFrame = CFrame.new((rootPart.CFrame.Position)) * CFrame.Angles(0, math.rad(cameraAngleX), 0) * CFrame.Angles(math.rad(cameraAngleY), 0, 0)
		local cameraCFrame = startCFrame:ToWorldSpace(CFrame.new(cameraOffset.X, cameraOffset.Y, cameraOffset.Z))
		local cameraFocus = startCFrame:ToWorldSpace(CFrame.new(cameraOffset.X, cameraOffset.Y, -10000))
		camera.CFrame = CFrame.new(cameraCFrame.Position, cameraFocus.Position)
	end)
end)
 
local function focusControl(actionName, inputState, inputObject)
	-- Lock and hide mouse icon on input began
	if inputState == Enum.UserInputState.Begin then
		UserInputService.MouseBehavior = Enum.MouseBehavior.LockCenter
		UserInputService.MouseIconEnabled = false
		ContextActionService:UnbindAction("FocusControl", focusControl, false, Enum.UserInputType.MouseButton1, Enum.UserInputType.Touch, Enum.UserInputType.Focus)
	end
end
ContextActionService:BindAction("FocusControl", focusControl, false, Enum.UserInputType.MouseButton1, Enum.UserInputType.Touch, Enum.UserInputType.Focus)
#24

There are a few ways to achieve this.
I like the most to use without changes to the Camera Module and without lots of CFraming since BodyGyro assists with the rotation.

Here’s the full topic about this: