JYH
“Generating” a ticket means buying one, which wouldn’t make any sense if also using a Swiss Travel Pass day.
Generally I wouldn’t recommend “wasting” a STP day just for Zurich - Basel anyway, especially with “smaller” STPs up to 8 days. A regular full fare Zurich Airport - Basel ticket is CHF 41.-, while e.g. a 6-day STP is roughly 64.- per day. My former employer would have refused to refund expenses for a more expensive “ticket” than the regular tariff.
Maybe consider a STP Flex and use regular tickets for those “business” related trips (1. class possibly allowed?) which you’d claim individually…?
Regarding proof of traveling in a train: There’s no “checkin” or “boarding” in any train, and there possibly might be no ticket control happening in the train at all. As a result, there’s no evidence of train usage available from SBB with online tickets.
A train ticket with a date and locations matching your flight, accomodation or meal receipts should actually be sufficient for your expense department. That’s how it is handled here, even at big multinational companies.