Use common sketch tools for manual placement of rebar shapes within a valid host.
Video: Detail with Planar Rebar
Rebar sketches will map to an existing shape when they share the following attributes:
If the sketch does not match an existing shape, a new shape will be created in the Rebar Shape browser and Rebar Shape type drop-down in the Options Bar.
Reinforcement panel
(Rebar).
Placement Orientation (or Placement Perspective) panel

Sketching a rebar shape

Adding rebar hooks to the sketched shape

Mode panel