Hi @baran!
You might want to try using JSON.parse. In your JS query you can do something like
return JSON.parse('{"_id" : {"$in": [{"$oid":"your_oid_here"}]}}')
Or, you can pass {{ JSON.parse(getIdList.data) }} to your MongoDB query.
As a side note: you might also try using the additionalScope object here. In your JS query you can trigger your MongoDB query with
var idList = idListInput.value.split(",").map(id => ({$oid: id}));
userQuery.trigger({additionalScope: {idList}});
and then in your MongoDB query you can write
{ _id : { $in : {{idList}} } }
Let me know if any of the suggestions here work 