Essentially you can reference any specific row and cell without a filter.
For example:
And then in any formula when needed just use an @ reference.
This will reference the specific cell in a table and once linked will adjust even if you empty or modify the content of that cell. Note that deleting the table row will break the reference.
You can find more into on references here.
If this is not what you are looking for or you need further assistance please create and provide a link to a test doc (clear of any personal data). We can then get a better idea of what you are after and can give more specific solutions.