1) Go to C: \ Program Files (x86) \ Steam \ steamapps \ common \ People Playground

2) Search ControlScheme and open it with notepad

3) Find "flipSelectedObjects-zooi": {
"HoldRequired": false,
"Key": 114, <-- here put the number of the letter, remember dont delete the comma
"SecondaryKey": 0,
"Universe": 2

4) For the number can you see this table, put the number of the letter in "Key": (number), and dont delete comma

32: Space
97: A
98: B
99: C
100: D
101: E
102: F
103: G
104: H
105: I
106: J
107: K
108: L
109: M
110: N
111: O
112: P
113: Q
114: R
115: S
116: T
117: U
118: V
119: W
120: X
121: Y
122: Z