Inconsistent Behaviour of keyboard shortcut CTRL+D

When viewing a list of references in a given group, I typically add the reference to some other group and then I use CTRL+D to remove the reference from the original group. This does not delete the reference entirely.  By that I mean it does not move the reference to “Trash”.  It merely removes it from the group.

However, if I use the search function on a given group (using the option "Search showing references) , I then get a list of references in the group that meet a certain criteria (e.g. search abstract for “intervention”)…working through this subset of references…I add a reference to another group and use CTRL+D  to remove it from the original group…, now it actually deletes the reference entirely.  It moves the reference to the “Trash” and removes it completely from both the original group and the group I moved it to.

I have checked the documentation on keyboard short cuts…I don’t see where CTRL+D operates as a “delete” function.   

I think this is a bug.