You can move selected objects as a group, without changing their relative positions. To do this, place the mouse pointer inside a shape or on a blank spot on a line that is part of the selected set and then drag to the desired new location.

You can perform any of the normal edit operations on a set of selected objects, just as you would for a single object, using either the shortcut key or the Edit menu. For example, to Duplicate a set of selected objects, select Edit / Duplicate or press Ctrl+D. A copy of the entire set of objects will be created on your canvas, just below and to the left of the original objects. Note that when you Duplicate or Paste a set of objects, after the operation only the newly-created objects are selected.

Due to limitations in the implementation some operations on single objects in a selection were still only modifying the single object. Since dia 0.97 these inconsistency got resolved so the properties dialog allows to change multiple objects properties at once - without first grouping them.

Also the single objects handles change behaviour in a selection (shown by slightly dimming them). Instead of resizing the single object they can just be used to move the whole selection an align it on the grid, see snap to grid for details.

	When pulling up the properties dialog, be sure not to double-click on the blank canvas or all of the objects will be deselected.

As noted above, it is easy to create and remove sets of selected objects, and a selection can be removed accidentally by double-clicking on a blank area of the canvas. If you wish to keep a set of selected objects as a permanent group so that you will not accidentally deselect them, you can create an object group. Just select Objects → Group to create the group. You can select Objects → Ungroup to remove the group. See Grouping Objects for more information on groups.