The EXTEND command extends objects to meet other objects.
In AutoCAD MEP 2023 toolset, EXTEND works on duct, pipe, cable tray, and conduit segments, and plumbing lines. However, fittings are not automatically inserted. To have fittings inserted automatically based on the preferences in the drawing, use Add grips instead.
You can also extend plumbing lines and schematic lines using the FILLET command.