Could you give us a bit of a preview about the changes regarding external editors? It would be helpful to know what the changes are before going ahead with the update.
> Message: 1
> Date: Mon, 4 Feb 2019 15:36:12 -0800
> From: Richard Koch <[hidden email]>
> To: TeX on Mac OS X <[hidden email]>
> Subject: [OS X TeX] TeXShop 4.24
> Message-ID: <[hidden email]>
> Content-Type: text/plain; charset=us-ascii
> TeXShop 4.24 is available via the Sparkle update mechanism and from
> http://pages.uoregon.edu/koch/texshop/texshop.html >
> If you use an external editor with TeXShop, it would be a good idea to read the Changes document in the TeXShop Help Menu about version 4.24.
> Dick Koch
> [hidden email]
School of Biological Sciences
University of Utah
257 South 1400 East
Salt Lake City, UT 84112-0840
To summarize, you can theoretically sync from the TeXShop Preview to your external editor, provided your editor has appropriate connectivity code, and if you typeset using TeXShop, then "Goto Error" in the Console can also sync to your external editor. I'm investigating the reverse sync from your external editor to the TeXShop Preview, but that is not yet in TeXShop (or even designed yet).