What is the best UI/UX Design for updating existing value in a particular field or creating new value for that field against unique ID in DB from an Interface?

Do you have a specific use case in mind?

In a record context we typically try to use related actions to modify data. Even better would be to modify data in an actual business process flow.

docs.appian.com/.../Records_Tutorial.html

I have a use case in which there is master table for A Field which contains records of 3 other table's filed B, C & D as per below screenshot. Table A has a field that needs to be created or updated and for other fields B, C & D user can do same thing.

A Contains master data of all A, B, C & D and B,C,D are child tables.

Do I need to user custom picker field for this because field contains more than 1000 values for each.

Please suggest.

I have a use case in which there is master table for A Field which contains records of 3 other table's filed B, C & D as per below screenshot. Table A has a field that needs to be created or updated and for other fields B, C & D user can do same thing.

A Contains master data of all A, B, C & D and B,C,D are child tables.

Do I need to user custom picker field for this because field contains more than 1000 values for each.

Please suggest.

Using a custom picker might be a solution. You can also create a record for the secondary tables und use a record picker.

Thanks Stefan