The shape behavior can be set via the context menu:
Behavioral Aspects are available only for standard shapes to convert them into containers or make grouping more easily. Elements of the modelling notations (such as Swim Lanes) have the Container property by default and therefore do not provide the Behaviour
context menu.
Sometimes it happens that you want to move or delete elements on the canvas and this does not work. Keep in mind that you or a colleague may have changed these form behaviors.
If you make an underlying rectangle to a container, make sure that you also move elements that are above this rectangle into the container (by drag & drop) so that they remain in their position and become a part of the group. This is indicated by a blue line.