Try this one, and tell me if it works…
async function get_bigData() {
var DB = "MyItems"
var ColTotal, COLLECTION = []
var multiplier = 1000
var countDB = 3
for (i=0; i<countDB; i++){
COLLECTION[i] = await wixData.query(DB)
.limit(multiplier*i)
.skip(multiplier*(i-1))
.find();
if(i>=countDB) {
ColTotal=COLLECTION[0].items.concat(COLLECTION[1].items).concat(COLLECTION[2].items)}
}
return ColTotal;
}