Thank you a lot for your answer, it really makes things clearer.
I tried to use triangulation of contour with holes
option as suggested and am getting some positive results. Seems like I catch a node of an internal column, but columns themselves get deleted after this operation. I must be using the command in a wrong way? Say , I have a meshed panel and want to add a column somewhere inside the panel. I add the column, then select contour with holes
command and it lets me to select one node in XOY plane. After clicking apply command it brings me to a new window where I need to add a new contour and input additional nodes. After this is done, the slab is re-meshed and the internal column is now sitting on the mesh node, but the new mesh is drawn over the old mesh and after coming back to the main FE model all the columns are deleted.
I have reviewed the tutorials in the last few days, but in all cases (as far as I remember) the columns are placed on the nodes of a panel mesh and therefore I could not find an answer there.
I am attaching few pictures and model for easier communication. Thank you again.