in bitcoin core, how to use Tor for broadcasting new transactions only? I have set up a full node with bitcoin core running on the internet.  I have also set up a wallet running on a private machine that communicates to the full node to broadcast new transactions.
To enhance privacy, I plan to enable Tor on the full node.  However, it is not clear to me how to use Tor only for broadcasting new transactions from my wallet.
Many tutorials tell you how to use Tor exclusively for everything.  That is not very good, because it wastes bandwidth, is slow and does not help bitcoin community.
Some other tutorials talk about using both Tor and IPv4/IPv6 at the same time.  However, with this setting it is not clear whether new transactions from my wallet are sent out via IPv4/IPv6 or not.  If they do, then you don't have much privacy after all.
Appreciate any pointers on this.
You cannot.
The node side of Bitcoin Core treats wallet transactions as any other transaction. They aren't treated any differently from transactions received over the network. So once the transaction is added to the node's mempool, it will be broadcast to connected nodes in the same way that any other transaction would be relayed.
All you can do is to temporarily run Tor only for transaction broadcast.