I was able to get the date selector in the header by using this code:
header_cards:
justify_content: null
cards:
- type: energy-date-selection
card_mod:
style: |
ha-card {
--ha-card-background: "rgba(30, 30, 30, 0.0)";
--ha-card-border-width: 0px;
--ha-card-border-radius: 1px
}
