Hi @Parth_Gupta
check your screenshot, list1 is actually meant to contain an array named "list" with the individual items, each of the form (and don't ask me why Adobe made it so complicated)
{
"value": "some value"
}

With your sample string (parts of it, I was too lazy to replicate the whole), a list1 data element could look somewhat like this
let list1 = {
list: []
};
const listData ="cif_2|accountNumber_108|sourceChannel_Branch|sourceChannel_API banking|sourcechannel_businessONLINE";
listData.split("|").forEach(item => list1.list.push({value: item}));
return list1;
Hope that helps
Cheers from Switzerland!