WP custom field options. How to write Custom field label?

Question

WordPress

I write ajax generation of arbitrary fields directly by the user "on the fly".
When creating, using the add_post_meta( $post_id, $meta_key, $meta_value, $unique ) function, we drive in the post id, key, value and uniqueness)
Question: where, how, and where is the label (Name) driven in?
If it is driven in as a key, then it turns out that if the user wants to edit only the name of the field, the script must change the key ($meta_key) - and this is, in fact, creating a new and deleting the current (changing) custom field?
Or is the label of an arbitrary field somehow and somewhere prescribed?

Answer 1

Label in this case is just a string that you display in the UI? That is, each created field will have 2 "parameters" - label (what is displayed next to the field) and value (what is entered in the field)? I see another bottleneck here - when you get to fields of other types (number, radio, checkbox, etc.), then you will have additional "parameters" - the field type and other properties. And here everything will become much more interesting :)
There is such an option - to store 2 records for one field in postmeta at once:
fieldname => field value (value)
fieldname_label => label value (label)
Fields can be named differently. For example:
fieldname => value
_fieldname = label
In this case, the field that starts with an underscore is considered "hidden" and "system". You can add a suffix. Well, then you need a bunch of "subsystems" to make it convenient to work with.
And there is another option - to store all (any) necessary information in the field value as a serialized array. The obvious disadvantage is that it will be difficult to search for such a field (however, external indexing using the same Elastic Search will solve the problem). For the rest - shove whatever you want there - the value of the field, its label, placeholder, character limit, and so on. Yes, even the entire html.