Some blocks in App Inventor are called dropdowns. What this means is that these blocks can be changed to mean or do something else by just clicking on the name of the block.
Some blocks in App Inventor have a small arrow facing down directly to the right of the block name. This arrow indicates that the block is a dropdown. When you click on the block name, a dropdown menu will appear with options of different blocks that your block can change to. See the figure below for an example.
Many of the blocks in App Inventor are dropdowns. The most notable ones include several different Math blocks, get and set, and getting/setting the properties of components.
If you ever can't see a block you need in the drawer, it could be because it is a dropdown of a different block. Try typing it on the screen to see if you can find it. It is important to know that dropdowns eliminate a lot of the blocks from the drawer but they are still available in App Inventor.
There may be a case where you need to do the same set of blocks over and over again with one minor difference. To make it easier, you can just copy-paste the blocks and make the minor change on one of them by using a dropdown.