Suggested by lukeeexd:

I have a Vanilla Survival server (or semi because it runs paper) we have a lot of shops, I mean a lot. 3 floors of nether with shop plots, in total 72 shop plots, each person can have as many shops in their plot as they can fit https://i.imgur.com/I3jfeJn.jpg. It gets hard to find what items you want
So my idea was, a command that opens a gui and you have the option to see players shop, or browse by item (separate feature request ticket: #601).

If you open the player shop one it will list everyone with a shop, you click their name it shows all their shops and what theyre buying/selling.

If you open item browse it shows every item being bought, sold or traded for how much and by who.

My remarks:

There is already a command for listing all shops, or the shops of a specific player. Maybe that could either be extended or replaced by an option to open that list as gui. I can also see the use of 'going one deeper' and listing which items they trade.
However, since I am not sure whether it is possible / how easy it is to display localized/user-friendly item names (ideally without maintaining a big list of localized item names or relying on other plugins to do that, such as Vault), any representation of items / trades would have to not rely on those. One could for example display them in the same way as they are displayed inside the editor menu (one 3x1 column per trade with buttons to scroll through the pages).