No, there is not a dotnet add-in, just using dotnet in C/AL.
There is an old version of a renumbering tool on this blog. It works in the classic client but who uses the classic client any more ?
I wanted to upgrade this tool to NAV 2015 (and NAV 2013 R2). There where a few issues that I needed to handle. First; how to upload a large object file to the server, how to read through millions of lines to find what I was looking for, how to replace string in all these lines without having to wait for days.