Hello. I haven't much experience in Houdini and I'm not sure what I'm doing right, because I'm getting too many Edit nodes in my object. Can I do the editing operations (Scale, Move, Rotate) inside PolyExtrude?

Too many for what? I think Houdini creates as many edit nodes as needed, no more, no less.
Inside the polyextrude param. window check “Transform Extruded Front” for transformations within extrude node.

McNistor
Inside the polyextrude param. window check “Transform Extruded Front” for transformations within extrude node.

Thanks, that's what I need.
And can I to merge several nodes, when they become too much? For example to freeze current state in one node?

you don't have to worry about this, you can have hundred of nodes in a network.
if you want to ‘freeze’ your work:
save out the last node using RMB > Save Geometry (or use a ROP Output Drive)
then read the geometry back in with a file SOP
but don't delete the network - if it isn't being used it can just sit there.

Strange how this was a concern for us when we moved over to Houdini. Now we love every edit node in the network. The best history you can get in any 3d application.

The fact that I can get confused when many of the same components.