Too many fish displayed? Wish you could just show a single patch? Try double-clicking on the patch number to display just the fish from that patch! (You can toggle other patches by clicking on them as well). You can also single-click the expansion button to toggle an entire expansion from being displayed.
Having trouble picking out those super rare fish from the vast list of upcoming fish windows? Now you can sort by Overall Rarity. As always, the rarest fish currently available will be shown first, followed by the sorted list of fish coming up in the next 15 minutes. But after that, the remaining fish will be sorted by rarity first, making those super rare fish jump to the top (even if they are days away.) I hope this helps you plan out catching the super rare ones. Good luck!
Another tool you may find useful for researching is the Weather Forecaster app. It can display all the possible weather transitions for a zone, as well as when each transition will occur. Some are much more rare than others.
Partial localization support is here! Select the language to change the in-game names and locations to your client's language. I'm very sorry the UI does not automatically translate well, please forgive me.
You can display the next 10 upcoming windows by clicking on the in front of the uptime text. You might be sad afterward though, looking at you Bobgoblin Bass...
Many fish, especially those requiring mooching, have hooksets associated with them. To make the display a bit more consise, you should interpret the badges as, when using this bait, use this hookset to reel in catch.
You can display the map for a fishing spot by clicking the in front of the location name. Use the scroll wheel to zoom in or out, and drag the map to pan around. Clicking on the name itself still opens a new tab linking to Garland Tools.
As of Patch 5.4, the Fish Eyes action removes the time restriction from non legendary fish introduced prior to Stormblood. Clicking the Fish Eyes icon will toggle this mode on and off. You can tell it's on when the icon has a circular halo around it and is fully colored.