Bitrix question about custom import module and binding via id?

Question

1C-Bitrix

There is a site on Bitrix, with staff and departments in which the staff works. Personnel is imported through a custom module (self-written). There is a section of departments in which staff is linked to the elements in the admin panel. Since the module for importing (uploading) personnel to the admin panel is self-written, the functionality of this module is as follows: An xlsx file is uploaded, the old section with personnel is completely deleted, and then a new section with personnel is generated. After that, all attached personnel in the departments are destroyed (because the import destroys the old one and generates a new partition). The question is - what can be done so that the associated personnel are not destroyed after import, will the import module have to be completely redone, or are there easier options? (for example, each staff has a special code - can make a binding on this field?, i.e. to ID when importing each time different, and special. codes are all the same).

So far I have settled on what to redo the import so that the old section is not deleted, but does update () of the corresponding elements