Hello, Todd.

Thank you for contacting us.  When you install Safari Technology Preview, it apparently copies its Bookmarks.plist file, which contains the bookmarks, and probably other stuff, from the regular Safari.  But it creates its own files and there is no synchronization beyond that point in time, unless, and I've never tried this, maybe they would sync if you switched on System Preferences > iCloud > Safari.  On the one hand, it seems that there should be some way to test Safari Technology Preview with iCloud, and there is only this one switch in the system.  But on the other hand, I don't imagine how the under-the-hood daemon process would handle two Safaris because it has enough trouble with one on some days.

Anyhow, if you give that a shot, let us know what you find.  Switch on iCloud, add a bookmark to one Safari, wait a few minutes, well maybe 15, then see if it shows up in the other Safari.  If it does not, see which Safari syncs to your other devices if you have any.  My guess is that only the regular Safari would sync to iCloud, but we really don't know until we test it.

Our apps don't support Safari Technology Preview in any way right now, although it might be possible to add without too much difficulty, depending on how iCloud factors in.