SciFi writer here and it’s a part of our genre that we italicize our spaceship names…
Is there a way to do a global search for a ship name say - USS Marathon – and then have the app make it change from plain text to italicized text throughout the whole book?
Now that would be cool…but I can’t seem to find that as yet in the app…
???
This is one of the many reasons why I use Markdown to write—no need for programs to have fancy and complicated features to adjust formatting. Just search for Boat and replace with Boat, done. 
Otherwise, nope that isn’t possible. Best you can do is get really familiar with F3 (find next) and Ctrl-I (italicise). Some people just wait until post-compile when they are finishing up the work in LibreOffice/Word/etc., where these kinds of tools are more often found.