Can SSRS RDL contents be modified in a text editor by changing the Parent property?

This is my question, I have an existing heavily modified SSRS report – lots of container objects (Rectangles inside Rectanges, Rectangles inside Tables, etc.). This was in 10.1.400, but upgraded to 10.2.300 and I cannot effectively re-create all the Container Objects to be the same. Once you create Rectangle Container Object, it references a “Parent” and it becomes grey-outed the Properties.

That being said, is there a way to “manipulate” the RDL internally to change this “Parent” to point to something else?

Alternatively, is there somehow/someway to take an older “working” RDL and get it to work in a newer version. The DataSet has the same name, just that there are additional fields that were added to that DataSet. Trying to re-create this customized report in the 10.2.300 has been a nemesis for me and just looking for ideas how to make it work like it did in 10.1.400.

It should work out of the box? Just re-create the RDD to be the same as it was in 400

Its modified a heavily modified APCheck (working in 10.1.400). I did re-create it 10.2.300 and thought it was working 100% and I had tested it with a single vendor payment, multiple invoices. Works great!

BUT, when the report is run with multiple vendors, multiple payment, multiple invoices…it sums up all the invoice amounts and places that grand total on each and every Check Face. It is somehow not aggregating /grouping by payment number and it is driving me crazy. It has something to do with the Rectangle Objects the Calculated fields not working (ie not grouping/breaking on the Payment Number).

I am running out of ideas why this is not working correctly.

Yes you can (contrary to the experts at Epicor tech support say).
A text editor can be used to modify everything in the RDL (as it is just XML), including the report objects to the exact values/parents you would like.