Lazarus 1.6.2, FPC 3.0.0, Debian Jessie, XFCE 4.10
I have a "Show a single button in Taskbar" enabled.
When I try to "move" Lazarus to "Another Workspace" not all windows are moved. What windows were moved depends on whether the Lazarus Main Window was active or not. If it was active - only the Main Window is moved. Else, all editor windows, object inspector, terminal output and messages are moved too, except for forms.
See screenshots.