The Path-effect "Offset" will work on groups - but I doubt the result is what you´re after. If you want say a cutting line like for a sticker around a bunch of grouped elements I´d go this way:
1. Draw a rectangle larger than the whole group
2. Zoom to selection (3) to max out the view
3. grab the Fill bucket tool (U) and fill the area between rectangle and group
4. give it a stroke/no fill
5. delete rectangle - take node tool to select a node from the outer rectangular shape - Edit->Select All ->Delete
6. you´re left with a contour around the group which you can now offset with Path->Outset/Dynamic Offset etc:
Beginners' Questions Is it possible to outset a group?
Inkscape.org
I'm trying to perform an outset on a group, is that possible?
The Path-effect "Offset" will work on groups - but I doubt the result is what you´re after. If you want say a cutting line like for a sticker around a bunch of grouped elements I´d go this way:
1. Draw a rectangle larger than the whole group
2. Zoom to selection (3) to max out the view
3. grab the Fill bucket tool (U) and fill the area between rectangle and group
4. give it a stroke/no fill
5. delete rectangle - take node tool to select a node from the outer rectangular shape - Edit->Select All ->Delete
6. you´re left with a contour around the group which you can now offset with Path->Outset/Dynamic Offset etc: