Yes you can. Here’s mine:
# Multiple networks with DHCP
wifi:
networks:
- ssid: Kaywinnet
password: !secret wifi_password
- ssid: Serenity
password: !secret serenity_password
- ssid: Naboo
password: !secret naboo_password
But your secrets.yaml has a problem. (Note, I am YAML-challenged and not an expert).
The secrets file is a list of substitutions using the format:
key: "data"
and you are using the same keywords more than once. I don’t think it will throw an error, but only the first key will be used.