Thanks for your reply.
I played around with it and I finally got it: I had set some fields via "
Tools -> Options -> Library & Folders -> Standard Library Fields" to be displayed with an other label (eg. I had the "
Name" field set to "
Title"). I set this a long time ago and it didn't make any problems until one month ago or so. For testing I tried to use the original field label (eg. "
Name") and my personal ones (eg. "
Title") within the smartlist editor. For some reason MC uses the original label for some things (eg. for sorting rules in smartlist editor, or the move/copy fields function) and the personal label for some other (eg. for the dup-rules in smartlist editor, or the step 1 in view ssheme editor). But neither nor worked.
Changing the labels back to default (via options) did the trick for me and now everything works again. So I think there is a bug, which was bothering me up for a month
Maybe there are some other things, as you mentioned eba, but now everything seems to work for me...