Sometimes I group several elements to move the whole thing. The problem I encountered is simply that all elements will be moved into the same layer as soon as I group the elements. Is there any way to avoid that behavior?

No, SVG does not have layers. Inkscape emulates layers with grouping and SVG only allows objects, paths, and other groups to be in one group. That is, only trees of groups are allow. Maybe, one day SVG will have layers. Until then, groups can not cross layer boundaries.

Well, nevertheless, if you group several elements, that reside in different layers (even though layers are really special groups), all the elements are moved into the same layer. There's no way to avoid it, but there IS a way to move them all at once. And that is simply to select them all, and rather than click Group, just move them. They will all be moved together. I know it's not a perfect solution, but you just have to use a different workflow to avoid grouping across layers.

Well, the problem with that is that I sometimes have more than 10 elements I want to move. As soon as I select something else I have to select 10 elements one after another again. Thats especially annoying when I want to move several elements above other elements. When I group those elements I just have to select the group, which is much more comfortable and not so time consuming. But if I want to change something within the group everything is in one layer. So I have to move Elements in different layers again which is very much annoying when I want to group it again. Infinite loop...

When Inkscape can emulate layers, as long as you don't group them, why can't it emulate the layers when you group them? Hopefully that will be different in a future version.

I don't know if it's been reported as a new feature/wish list "bug" or not. But you could search at Launchpad, Inkscape's bug tracker: https://launchpad.net/inkscape Or maybe ~suv will chime in here? If it's a reasonable option, then you could make the request yourself.

Wicket wrote:When Inkscape can emulate layers, as long as you don't group them, why can't it emulate the layers when you group them?

Read the earlier explanation given:

shawnhcorey wrote:Inkscape emulates layers with grouping and SVG only allows objects, paths, and other groups to be in one group. That is, only trees of groups are allow.

An object cannot be a direct member in several groups across trees at the same time (it is kind of "in several groups" within the same tree when groups are nested, but not as direct member either).

And yes, it's a well known limitation - Inkscape is waiting for SVG to have real layers included in the specification (see the Wiki page SVG Working group listing how the SVG standard can be improved to the benefit of Inkscape).

Secondly, based on your described workflow issue, more likely you don't really want grouping across layers, you want (named) selection sets: see the feature request “sets (named selections)” in the bug tracker.