I first thought this amazing trick would do, but I can find no way of setting overlays relatively to one specific event: my dream:
% <:name:XXX> would mean "use overlay specification XXX and label
% corresponding pause as `name`".
% <(name)XXX> would mean "use overlay specification XXX relatively
% to pause `name` and not to zero.
\begin{itemize}[<+->]
\item first \visible<(anchor1).(1)->{fourth} % one after anchor1
\item second \visible<(anchor2)->{fifth} % exactly anchor2
\item<:anchor1:+-> third \visible<(anchor1)+->{fourth} % one more after anchor1
\item fourth \visible<(anchor1)+->{fifth} % one more after anchor1
\item<:anchor2:+-> fifth \visible<(anchor2)+->{sixth} % one more after anchor2
\item sixth \visible<:anchor3:(anchor2)+->{seventh} % one more after anchor2, label this `anchor3`
\item seventh \visible<(anchor3)+->{eighth} % one more after anchor3
\end{itemize}
Does this somehow already exists?
How hard would it be to implement?
How many times would it require the document to be compiled until stabilization?
Obviously, responsibility for non-looping specifications would be left to user.
