He means the button you see when facing for example a sheep, the button that shows up to cut off the wool.
Btw post updated also since the words in pic is random it seem to not be client sided like i thought maybe worth checking fishing rod's code since on there it somehow sent the Fish popup so it isnt entity dependent either
There are no API methods for doing this currently. However, you can do the following: PHP: $entity->setDataProperty(Entity::DATA_INTERACTIVE_TAG, Entity::DATA_TYPE_STRING, "whatever_you_want_on_the_button_here"); Please however be aware that this will change in the future when entity implementation is rewritten.
@Thunder33345 Good question, haven't the foggiest on that one. PocketMine lacks so many gameplay features it's difficult to test this stuff.