Select all adjacent floor surfaces

`↑ Shift` + `U`

All hotkeys for Unreal Engine

Viewport navigation Movement (Standard)	`Mouse movement`
Viewport navigation Movement (Standard)	`Mouse movement`
Viewport navigation Movement (Game-style)	`Mouse right click` + `W`
Viewport navigation Movement (Game-style)	`Mouse right click` + `A`
Viewport navigation Movement (Game-style)	`Mouse right click` + `S`
Viewport navigation Movement (Game-style)	`Mouse right click` + `D`
Viewport navigation Movement (Game-style)	`Mouse right click` + `E`
Viewport navigation Movement (Game-style)	`Mouse right click` + `Q`
Viewport navigation Movement (Maya)	`Alt` + `Mouse movement`
Viewport navigation Movement (Maya)	`Alt` + `Mouse movement`
System-wide Find in Content Browser	`Ctrl` + `B`
System-wide Open Console	`'`
System-wide Open documentation	`F1`
Transformation selection Translate	`W`
Transformation selection Rotate	`E`
Transformation selection Scale	`R`
Transformation selection Next transform	`Space`
Common commands Copy	`Ctrl` + `C`
Common commands Cut	`Ctrl` + `X`
Common commands Paste	`Ctrl` + `V`
Common commands Duplicate	`Ctrl` + `W`
Common commands Delete	`Del`
Common commands Undo	`Ctrl` + `Z`
Common commands Redo	`Ctrl` + `Y`
Common commands Select all	`Ctrl` + `A`
Common commands Rename	`F2`
Viewport commands Lit view mode	`Alt` + `4`
Viewport commands Unlit view mode	`Alt` + `3`
Viewport commands Wireframe view mode	`Alt` + `2`
Viewport commands Focus on selection	`F`
Viewport commands Grid size decrement	`↑ Shift` + `[`
Viewport commands Grid size increment	`↑ Shift` + `]`
Viewport commands Perspective view	`Alt` + `G`
Viewport commands Front view	`Alt` + `H`
Viewport commands Side view	`Alt` + `K`
Viewport commands Top view	`Alt` + `J`
Modes Placement	`↑ Shift` + `1`
Modes Paint	`↑ Shift` + `2`
Modes Landscape	`↑ Shift` + `3`
Modes Foliage	`↑ Shift` + `4`
Modes Geometry editing	`↑ Shift` + `5`
Play world Play world	`Alt` + `P`
Play world Possess or eject player	`F8`
Play world Pause	`Pause`
Level editor Select all adjacent floor surfaces	`↑ Shift` + `U`
Level editor Select all adjacent slant surfaces	`↑ Shift` + `Y`
Level editor Select all adjacent surfaces	`↑ Shift` + `J`
Level editor Select all adjacent wall surfaces	`↑ Shift` + `W`
Level editor Select all coplanar surfaces	`↑ Shift` + `C`
Level editor Snap bounds to floor	`↑ Shift` + `End`
Level editor Snap origin to grid	`Ctrl` + `End`
Level editor Snap pivot to floor	`Alt` + `End`
Level editor Snap to floor	`End`
Level editor Find in blueprint	`Ctrl` + `K`
Level editor Gameview	`G`
Level editor Full screen	`↑ Shift` + `F11`
Level editor Immersive mode	`F11`
Level editor Jump to bookmark	`0` - `9`
Level editor Set bookmark	`Ctrl` + `0` - `9`
Level editor Show navigation mesh	`P`
Level editor Save all	`Ctrl` + `S`
Level editor Measure tool (orthographic only)	`Mouse movement`
Level editor Context menu	`Mouse right click`
Level editor (click transform) Duplicate & transform	`Alt`
Level editor Hide selected object	`H`
Level editor Unhide all hidden objects	`Ctrl` + `H`