Hi, Coda team! 
Thank you for your Coda product, I really like it and would like to suggest some improvements.
There is a great lack of the ability to select a specific field in related fields, rather than just one key field. The idea is, when we link the same database or different databases, we see the name of the key field.
I understand that it is now possible to change one key field, but only one for everything, but this is not the case, since the key field is required more as an identifier.
But in certain situations, I need to be able to determine the name of another specific field in this particular mapping bundle without changing the key one. This will allow for more flexible management of semantic connections.
At the same time, I suggest simply adding such a selection to the drop-down list, that is, it is a list of available fields in the linked database, but by default we show the key field.
I am sure that this is not a serious revision, but only the output of a link to a specific field that is associated with a key database.
Therefore, I hope my proposal will be appreciated and accepted for development, I look forward to an early update! 
Thank you! 
I’m not quite sure what you mean…
But if you mean a two-way edit of columns of related tables, it is possible by having the relation (B) displayed as a table INSIDE the linked row (A). This way you can change the values of the relation (B), by opening the row (A).
I am also not clear on exactly what you are looking for.
If it is something like an id (display column) and description, another field, I concatenate the two columns, and make the new column the display column. Then you can search in the new column using either the is our the description for the record you’re looking for. E.g. GL account number and gl description.
Perhaps I did not formulate it correctly, most of all, I want to see the value of another column through the associated field with the possibility of editing it. For example, you have one table, you create a two-way relationship, and you have a name in each of the created related fields. This is the name of the key column. I want to be able to choose the name of the field that I can select in the settings, that is, not the key field, but the one that I want from all those in the database, while for each related field, without changing the key field to another. For example, you have a table with columns: A (key field), B, C I create a relationship + D and E. In the linked columns, we see the values of the key column A, and I want to show the value of column B, and in field E, for example, C. The way I see it is, we go into editing the field and there is a link, that is, a field with a drop-down list of those fields that are in the database for selection. The same applies to the relationship between different tables. Of course, I can use a formula to extract the values of other columns for the key associated field, but this does not give me the opportunity to edit it, which means choosing a different value, since it is a formula. This is the advantage that we can see the values of other fields while maintaining the connection.
Please share a doc with an example as far as you have been able to set it up.
I am now more confused.
Is D & E in a new table, same table? How are the linked.
You’re not going to be able to do that. No database is going to have a function that allows a column to sometimes refer/validate to one field in a record, and other times to another field.
Yes, of course, I won’t be able to do that, so I sent a suggestion to consider the possibility of adding such a feature.
I believe that if we can see the value of a key column based on the value of a related column, then we can probably see the value of the same row, but a different column, because in the settings we could select such a column to display.
After all, this is just a column number, that is, the column number of the displayed value changes instead of the key column number. If there are already mechanisms for this in the form of formulas, as well as the ability to change the key column to display the value, then this means that this function can also be implemented, but this is my opinion.
I just suggested it, considering that it would expand the functionality of the product, and also make it much easier to solve problems if there were such functionality.
Thanks for the feedback! 
