You can’t template in every field. This is a field that is not templateable. Nothing in scenes is templateable. Try a script instead. Also a good rule of thumb: “If the field name or parent field name doesn’t have the word template, you can’t template there”.
example of a field name with the word template
value_template: "{{ ... }}"
example of a parent field name with the word template
data_template:
entity_id: "{{ ... }}"
I believe data_template is the only parent field that allows templating.