How can I add indentation in headings?

[sijo]

Does the following do what you want?

#set par(first-line-indent: (amount: 1.25cm, all: true))
#set heading(numbering: "1.1")
#show heading: pad.with(left: 1.25cm)

= #lorem(5)
== #lorem(5)
#lorem(30)

#lorem(30)