Also, something that's not directly mention, but not exactly hidden like Mouse 3 block picking is that in the F3 Menu, there is a list of binds accompanied with F3 Key that give easy shortcuts or life hacks such as showing chunks, clearing chat, etc. So easy trick to get around this is to do command such as setblock and then replace command with / tp so you can tp to those coordinates. This doesn't work with TP commands though, because the first use is to tp player by name and not coordinates. Besides the fact that you can fill in phrases and such for certain commands, you can also actually use Tab while looking at a block to shortcut it's coordinates. The feature within commands is that if you press Tab, you 'll fill in blanks for commands. But if you d like, you can steal banners off Endcity: 3 If you put an item in an item frame and attempt to pick at frame, you 'll get an item inside which is kind of neat. I think that's obvious, but in case you thought you could: same as endermen, you also cannot pick blocks off of shulkers. You also can't pick spawn egg off of mobs that don't have one. Baby Mobs are just smaller versions of that mob. You can't pick blocks they possess and you can't get baby mob eggs. Besides picking blocks, you can also pick at mobs and collect spawn eggs if they have one. But unusual blocks that you would normally not collect in your normal game or from Creative Menu, such as Dragon's Egg, or Barrier blocks, can be picked as so: while there are blocks that you can't get without commands that you can get with Mouse 3, there are blocks in game that are SPECIFICALLY not to be possess by player such as End Portal and End Gateway. You can't pick up blocks that change based on other blocks, such as snowy grass block. But though this isn't secret, there are a lot of neat things to do with it.
This isn't SPECIFICALLY hidden or secret, just not directly mention. If you press your middle Mouse button while looking at a block, you 'll pick that block into your inventory. Besides that, there are few neat Tricks hide features in Minecraft for Creative Mode that might help you next time you wanna make a castle out of cobble stone with a magma river surrounding it. In Minecraft, there are plenty of different jokes and easter eggs hide in the game, like Lie achievement referencing cake from Portal, or Vindicators's name Johnny go on rampage, killer rabbit, rainbow jeb sheep, upside down dinnerbone Mobs, etc.