After being told all about it by Peter Kahrel, I thought you might enjoy an update on the GREP capabilities since InDesign CS4. It turns out there are more and newer GREP code tricks supported in InDesign CS4 within its Find/Change dialog box.
GREP code seems to have stayed the same from CC 2017 down to CS5. InDesign CS4 supports many more GREP codes than InDesign CS3. I have added them to my handout sheet and it is available and freely downloadable here (CC) and here (CS6) and here (CS5). I have also added a 1-column version of this GREP list for convenient viewing on hand-held devices like the Apple iPhone, available here (CC) and here (CS6) and here (CS5). (InDesign CS5 adds a few new GREP codes beyond CS4, but CS6 and CC seem to have stayed the same.)
Many of the additional codes are for obscure text situations; many for asian and middle eastern language typesetting situations, too. Some of the more interesting codes allow you to search for all spaces, or just some kinds of spaces; all punctuation, or just some kinds of punctuation. It makes me glaze over just thinking about it! Why not visit Peter, and download his learning tools for these new tricks. http://www.kahrel.plus.com/indesign/grep_mapper.html
I would like to mention, too, that there is a second page in my downloadable handout that gives explicit examples of GREP search scenarios, along with notes on how to set it up to accomplish your typesetting goals. So download it and enjoy the learning. Get yourself warmed-up to this new feature of InDesign. We use this handout in our Washington DC-area training classrooms all the time!