How to capture filter on BLE address?

edit

See the links in my answer below that has links to the different filters and their syntax.

My take is that Wireshark capture filters use the Berkeley Packet Filter syntax

Yes, given that Wireshark (dumpcap, in particular) uses libpcap/WinPcap/Npcap to do packet capture.

which does not have any functions for filtering by BLE hardware addresses

...because nobody's changed pcap_compile() to support them; they could be added.

This is a display filter, and won't work for capture filtering. See my answer below.

I am! Now I know the btle fields don't work for capture. Thank you.

Nothing inherently prevents capture filters from existing for Bluetooth LE. To support it would require:

1. Whatever software connects Wireshark to the Bluefruit sniffer to support libpcap's BPF interpreter and BPF compiler
2. libpcap's compiler to support Bluetooth LE as a link-layer including the appropriate filter expressions.

The first of those would require the supplier of that software to change it; they should ask the tcpdump-workers mailing list, at [email protected], for help. The second of those would require libpcap changes; the same mailing list would be the place to ask for that. Please pass this information on to the supplier of that software (Nordic Semiconductor?).