What does the warning "Supported nodes No. 1-4 lie on supported lines as well" mean?
The warning should prevent doubled support conditions set by mistake - once as degrees of freedom on the node (nodal support) and once as degrees of freedom on the end point of the line (line support). A user can overlook the possible conflicting boundary conditions. Therefore, it may be useful to define different stiffnesses for nodal and line supports when modeling surface elastic foundations (see "wedge of soil" keyword in RFEM manual). If the support conditions have been set in this way for purpose, you can close the warning message by clicking "No".