Usecase1: mode = Cyclic
In this case by default there will be only <COUNTER> in LineEdit[automatically added] and this should be always at the end of the LineEdit and which should not be edited. But the user can insert new characters before <COUNTER>[All entries in the pop up list cannot be used by the user[shows warning on selection]

Usecase2: mode = Limited
In this use case user can add any place holder[<CONTER>, <DATE>, <TIME>, etc...] from the pop up list and all this can be editable[no restrictions] and user can insert new characters anywhere in the LineEdit.
LineEdit_Sample2.png