Hello Grenier!
It is not correct to translate “papañca” as “”making manifold.”
Papañca means to be “blinded by sensual pleasures” and to engage in highly-immoral deeds. One who engages in such thoughts, speech, and actions is bound to be reborn in the four lowest realms (apāyā.)
This is discussed, for example, in the “Madhupiṇḍika Sutta (MN 18)“.
For example, the following is a key verse there: “yatonidānaṃ, bhikkhu, purisaṃ papañcasaññāsaṅkhā samudācaranti. Ettha ce natthi abhinanditabbaṃ abhivaditabbaṃ ajjhositabbaṃ. Esevanto rāgānusayānaṃ … pe … etthete pāpakā akusalā dhammā aparisesā nirujjhantī’ti..”
Papañca is thus related to pāpa kammā. See #13 of the post, “Kusala and Akusala Kamma, Puñña and Pāpa Kamma”
– It is a good idea to read that post to get a good idea about the words, kusala/akusala kamma and puñña/pāpa kamma.