Design for back references

[SimonChaumet]

I don't know is it's the real name for it but I would like to create a flat model and use references but I don't know what's the good way to do it.

Here is my store for all my data models :

@model("TwoU/StoreCatalog")
export class StoreCatalog extends Model({
    themes: prop<Array<Theme>>(() => []),
    contexts: prop<Array<Context>>(() => []),
    scenarios: prop<Array<Scenario>>(() => []),
}) {
}

I receive data from my backend with nested objects :
[Theme]
|-- Contexts: [Context]
| |-- Scenarios: [Scenario]

Should I normalize my data before or fromSnapshot could create it automatically with custom references ?
Should I use onChildAttachedTo to create the objects or am I totally wrong ?

I could normalize my data but I would need to create a schema for normalizr that looks like the one for mobx keystone whish is redundant.

Thanks for your help.
@xaviergonz