Topic Title

Working only in 2D, when I use LinkEnts,
this command also migrates all the work to one layer.
I really don't want that.
What am I doing wrong?

From the manual:
Caution: When you group entities, DataCAD moves all entities in the group to the same layer. By definition, all entities in a group must be on the same layer.

Joesph is correct. But if you want to work on a multiple entities across different layers, Selection Sets are what you want to use.
You need to add them all to 1 of 8 possible selection sets, which you can also rename if that helps. When doing a move or other actions, you select the active set by using the mask feature.
You can quickly change the active Set in the Status Panel, or Alt-#.
I don't use often, but sometimes the come in handy.

Many many thanks for the answers!
Bob