Press Tab to grab the block under your crosshair.
If that block is already in hotbar slots 1–9, Tab switches to that slot. If it
isn’t, a single ghost item is placed in an extra § slot between the hotbar and
your offhand. The next Tab replaces that ghost item and never dumps it into
your inventory.
In Survival, Tab only selects a block you already have. The § slot is Creative-only.
Default keys: Tab to pick, § (the key left of 1) to select the extra slot.
Both can be rebound in Controls.
