Keyboard and mouse

On macOS, Cmd takes the place of Ctrl.

Anywhere

Keys Does
F1 Opens this guide
Ctrl+F Find in the open Blueprint
Ctrl+Shift+F Find in Blueprints, across the open folder
Ctrl+Shift+E Shows or hides the Explorer (folder mode)
Ctrl+` Shows or hides the Output Log
Alt+Left / Alt+Right Back / forward, after a jump or a search result (the mouse's back and forward buttons too)
Ctrl+= / Ctrl+- / Ctrl+0 Everything larger / smaller / back to 100%
Ctrl+scroll, over a panel Everything larger or smaller
Enter, in a search box Searches

In a graph

Keys or mouse Does
Right-drag, or left-drag on a node Pans
Scroll Zooms, up to 1:1
Ctrl+scroll Zooms in past 1:1, as in the editor
F or Home Fits the graph to the view
Click Selects a node; on empty space, clears the selection
Shift+click / Ctrl+click Adds a node to the selection / toggles it
Left-drag on empty space Selects with a box: with Shift it adds, with Alt it removes, with Ctrl it toggles
Ctrl+A Selects every node
Ctrl+C Copies the selected nodes, to paste into the editor (Copy nodes)
Double-click a node Opens what it calls: a function, macro or collapsed graph, in this or another Blueprint
Right-click Copy and Select All

In Time-lapse

Keys Does
Left / Right, with the pointer over the bar The older / newer revision

In lists and trees

Mouse Does
Double-click a Find result Jumps to it
Double-click a row with children Opens or closes it
Right-click a My Blueprint item Copy (a variable or a function, to paste into My Blueprint in the editor)
Right-click a Details row Copy the value, Copy Display Name, Copy Internal Name