Using INPUT() as a way to pass data to another table

[JpChapron]

Hello

I have been pointed out on how to use the INPUT() expression to pass data to another table, my use case was : 

Table 1  has multiple Fields, 1 of them is the client name, another is an ENUMLIST from a table that contains all Emails of Said client. With the possibility to add a new one :

I wanted to get rid of the Annoying "double entry" if a new email was entered, where you are in the form, select the client, then from the same form add a new email and it asks you AGAIN the Client name :

I was able to do that with the help of @WillowMobileSys  in this post : https://www.googlecloudcommunity.com/gc/AppSheet-Q-A/Reference-a-Dereference/m-p/485837#M191177. By using an action to "Set the data in some rows" and use the INPUT() Expression on the Email List Table, and on the "Main" table, setting an action "data : execute an action on a set of rows" then using the Action I created on the Email list table there. like here : https://www.googlecloudcommunity.com/gc/Tips-Tricks/Using-INPUT-to-update-another-table-using-a-valu...

Now I have a much more complicated use case.  For clarity, we will call the Table1 that has the open form "Host" not to be confused with references/dereferences

I want to do the same thing, pass the "Client Name" to a field in a Grandchild table, but to do so, I need to bind the "Input" action, to the "Host" table, my problem is, how would I reference My Grandchilds row ? I've tried using this : 

[Related Child].[Related GrandChild].[stuff that I need_ID]

But i'm getting this error.. : 

Column Related Routes in expression '[Related Child].[Related grandchild]' does not contain a reference

Now Obviously, there is something i still dont understand as to HOW to reference multiple tables together, question is : What? 

Does anyone know if it is possible to basically Pull data from the "Host" and send it to the "Grandchild" if this grandchild has a "New item" added to a dropdown?

thanks !

[Marc_Dillon]

[Related...] is a List of Refs, not a single Ref. You can't use the dot-notation to dereference a List of Refs. You can use List dereference, which just excludes the dot, like [Related...][col in child table], which will return another List. However you can't chain list dereferences, which means you can't do either [Related...][x][y] or [Related...][x].[y]

Also keep in mind that this field expects a List of Refs, not a single one. If by chance you're only giving it a single Ref value, make sure to wrap it in LIST()

You'll probably just want to manually construct a FILTER expression in this case. Perhaps something like:

FILTER( grandchild , [child].[parent] = [_THISROW] )

https://help.appsheet.com/en/articles/4575708-list-dereference

Edit. On second thought, I think [Related child][Related Grandchild] might be all you need?