The Linked Attachment Base Directory tells Zotero where to *look* for LINKED attachment files (that is, those not in local Zotero storage under Zotero\storage) when you try to open them ... when their parent folder location is different on different synced computers. https://www.zotero.org/support/preferences/advanced#files_and_folders
You set the LABD on each computer to the linked attachment files' parent folder location on that computer.
The LABD has no effect on where those attachment files get *saved* when added to Zotero.
https://www.zotero.org/support/preferences/advanced#files_and_folders
You set the LABD on each computer to the linked attachment files' parent folder location on that computer.
The LABD has no effect on where those attachment files get *saved* when added to Zotero.