BUT I NEED TO ADD MORE NOT TO CHANGE EXISTING OBJECT

this is still a really cool video

> maybe just, you know, use hammer and avoid all this unnecessary effort?

Nah
That would be too easy

maybe just, you know, use hammer and avoid all this unnecessary effort?

I haven't found a practical purpose for the Renderables section. I think it is for an internal use by the puzzlemaker. The other mysterious words control how the item works in the puzzlemaker.
For example, EmbeddedVoxels sets the both extent of the red-dashed blocking area (that may not collide with any other object), and the room that the editor carves into the wall using the backpanels_cheap texture for the object to be placed into. OccupiesVoxel=0 means another item may be placed in the same spot. ConnectionPoints lists the alternative coordinates relative to the item where the little indicator lights are placed and can be anchored. I do not have a good tutorial on these; usually getting the desired outcome is a matter of experimentation, and not all combinations of settings are even possible / supported by Puzzlemaker.

Yes, you would need to create custom 3DS models in order to have the item appear in Puzzlemaker as something other than a clone of some other unrelated item.

Thanks to this guide I have created some items (used in http://steamproxy.net/sharedfiles/filedetails/?id=504396998 and more to come ). It works with BEEMOD v2.5 and v4 also.
The problem with the created walls is that we cannot hang items on, and they hide antlines (indicator lights).
Other inconvenience in the editor, the absence of appropriate model; if we use many custom objects, in addition to those of BBEMOD, everything is confused. For that it would be necessary to create 3ds models (I think we have to use Softimage Mod Tool https://developer.valvesoftware.com/wiki/XSI_Mod_Tool) .
Otherwise I does not understand the difference before/after "Renderables" in editoritems; there is also many other mysterious words, like DesiredFacing, OccupiesVoxel, OccupiedVoxels, CollideType, CanAnchorOnBarriers...

Thank you

In maps that you create, yes. They work just fine.
IF your custom items depend on custom textures / models (i.e. vmt/vtf/mdl files that were not supplied with game), then things get more complex: You need to pack them in the bsp file, or otherwise people will see errors / magenta checkboard instead of these things. But within the instructions detailed in this video, this is not an issue. They work just fine.

Question: Can other people see your custom items?

Download the video subtitles, and there you have it.