Update: this issue applies to ANY SObject tab (Custom + Standard), too.
On all Orgs but one that I know at the Account tab there is a first option "+ New Account". It looks always like this and this is the expected behavior:
Now on one bad Org the Account tab just looks like that and the desired "+ New Account" option seems to be lost:
I am sure, that some time ago it was there. I can't remember that we have changed anything. On other tabs (e.g. Contact) the "+ New Contact" option is available:
Is there any way to get that "+ New Account" option back??