yq/pkg/yqlib/doc/operators/headers/comment-operators.md

Comment Operators

Use these comment operators to set or retrieve comments. Note that line comments on maps/arrays are actually set on the key node as opposed to the value (map/array). See below for examples.

Like the = and |= assign operators, the same syntax applies when updating comments:

plain form: =

This will set the LHS nodes' comments equal to the expression on the RHS. The RHS is run against the matching nodes in the pipeline

relative form: |=

This is similar to the plain form, but it evaluates the RHS with each matching LHS node as context. This is useful if you want to set the comments as a relative expression of the node, for instance its value or path.