You can use the Continuation grip in the middle of a header pipe segment to begin routing a branch.
You can create a branch using object snap to route into another pipe.
For precise placement of the branch segment, you can select and move the branch fitting up or down the header. The connected branch moves with the fitting.
The branch table in the pipe spec identifies the fittings (if any) and fasteners that are used when you connect to another pipe. For example: a tee when connecting to a pipe of the same size, or an o-let when branching to a smaller pipe. For more information, see Modify Branch Tables.