When kcfg entries are set immutable [$i], disable the corresponding UI Item.

The Show animation when switching's checkbox consolidate all the effects listed in [Plugins],
consider if one is set to immutable enough to disable the entry in the UI.

All entries are located in kwinrc

• To disable the modification of the desktops' list,

[Desktops]
Number[$i]=2
Rows[$i]=2

• To disable the Options part

[Plugins]
cubeslideEnabled[$i]=true
desktopchangeosdEnabled[$i]=true

[Script-desktopchangeosd]
PopupHideDelay[$i]=800
TextOnly[$i]=true

[Windows]
RollOverDesktops[$i]=false