  With the proliferation of VR and a metaverse on the horizon, many multi-user
activities are migrating to the VR world, calling for effective collaboration
support. As one key feature, traditional collaborative systems provide users
with undo mechanics to reverse errors and other unwanted changes. While undo
has been extensively researched in this domain and is now considered industry
standard, it is strikingly absent for VR systems in research and industry. This
work addresses this research gap by exploring different undo techniques for
basic object manipulation in different collaboration modes in VR. We conducted
a study involving 32 participants organized in teams of two. Here, we studied
users' performance and preferences in a tower stacking task, varying the
available undo techniques and their mode of collaboration. The results suggest
that users desire and use undo in VR and that the choice of the undo technique
impacts users' performance and social connection.
