The Pick Block mod is a little tweak that streamlines your Minecraft experience. If you click or use a chosen keybind on any block or entity, provided you have that item anywhere in your inventory it will automatically jump to whatever slot you’re currently using in your hotbar. So say for example you want to use some stone blocks as your next item to build with. If you see some stone nearby, just use the keybind for this mod and it will move to the highlighted slot in your hotbar.
It also helps if an enemy is closing in and you don’t have a weapon ready. If you use the keybind while sneaking, then the best weapon in your inventory is suddenly ready to use.