Some aspects of gradual development were collected in this thread:
But, these conditionality chains are not called āgradual pathā or āgradual trainingā in the SN, as far as I can tell. Even in the AN itās not quite the same as what can be found in the MN; most references are to the general fact that progress is gradual without setting out detailed stages.
I think the Gradual Training lists in the MN & DN were built from the SN & AN. On that note, something quite interesting was pointed out in another thread:
notably contrary to this sequence: mindfulness and clear comprehension -> restraint of the sense faculties -> the three kinds of good conduct
the order of the factors in the Gradual training is reversed: the three kinds of good conduct -> restraint of the sense faculties -> mindfulness and clear comprehension
but the order of AN 10.61 to me seems more logical and progressive notwithstanding the word āGradualā as a heading for the second one
SuttaCentral