Most of the time when placing nodes, you will use the Context Menu which can be accessed by Right-clicking inside a Blueprint graph.
From the menu above, you can expand any category (or sub category) and select the node you wish to add to the graph.
There is also an option in the upper right corner of the window called Context Sensitive that is enabled by default but can be disabled which automatically filters the options presented in the menu based on the current context.
As you can see below, when Right-clicking and searching for Animation with Context Sensitive on, you are presented with a filtered list.
However, if you un-check Context Sensitive and search for Animation, you are presented with everything related to animation.
While Right-clicking in the graph brings up the Context Menu, you can drag off an existing node to access the Context Menu as well.
Above, we have a Character Movement Component Reference and by dragging off its out pin, we can add nodes that contextually make sense and are relevant to the node we are dragging off of as seen in the example below.
Above we can set the character's Max Walk Speed by searching for Set Max Walk then choosing Set Max Walk Speed from the menu.