How to delete attribute records of certain subscribers(lots) to be able to use placeholders

I am trying to delete the attribute records of certain subscribers, to make these records blank.

I can delete these subscribers, and import them again, but then I lose all their history.
I cannot import them with those attribute fields empty because empty fields are not overwritten.
The subscribers are too many to do it manually.

I need these fields blank to be more flexible when using placeholders like [Country] for example.

Help will really be appreciated. Thank you in advance.

@Mailman99 The Subscribers plugin might do what you want. It has a command to empty an attribute value (setting the value to an empty string) for selected subscribers. See plugin:subscribers [phpList Resources]

@duncanc Thank you very much for your help. I had to upgrade my plugin to display this feature.

Thank you very very much.