Edge/Face extrusion

Tap Select menu > Edges or Sides, then Tap Select menu > Filter > side

Then select desired edge and click on Tools menu > extrude this will extrude the edge (creates new object)

When extruding you can Ctrl + E to extrude it again because when an edge/face gets extruded app automatically selects newely created edge/face, you may face some issues that Ctrl + E doesn't work - this is an android and bluetooth keyboard bug or you didn't select the proper window in the app.

That even when you have enabled keyboard it doesn't respond mainly because keyboard switches itself off and there is no way of keeping it always on.

You can also select faces in 3D mode and extrude them with same tool.