Linking old previous records

We are using the ERPNext for several years. currently we need to have all the PO’s & SO’s as will quotation and material request to be linked under one project.
the problem is to do so we need to delete the existing records.
now we don’t need to modify or change any of the existing records since it’s not practical alot of effort to be spent as well for quality purposes it shouldn’t.
but we should be able to link the records and changing the linking even for saved records and without the need to amend them.

kindly advice if this is possible soon.

or if you have a solutions.