all secret b recipes (that I found):
I + I + ccw U + ccw U
I + cw M
E + ccw U + ccw U
hm C + D + I
P + )
I + ccw W
hm C + I + ccw U
hm C + I + I + ccw U
hm C + hm C + E
hm C + ccw U + I
hm C + hm C + I + I
) + D + I
ccw U + D + I

bending 5 will give you an S :))

hm = horizontal mirror
vm = vertical mirror
cw = clockwise
ccw = counter-clockwise
dr = 2x rotation

"=" = dash + dash
@ = O + Q
@ = A + O
~ = cw ) + cw (
~ = bend cw+hm S
key = O + I + I + dash
key = O + I + dash + dash
key = O + vm F
key = O + L + L
key = K + E + Y
key = O + ccw L + ccw L
key = O + hm+cw F
key = O + I + "="
door = dash + O + vm U
door = D + O + O + R

hm = horizontal mirror
vm = vertical mirror
cw = clockwise
ccw = counter-clockwise
dr = 2x rotation

X = Bend K in any possible rotation.
% = All combinations of one I or dash + (2 O's or an 8 or a rotated 8)
& = ( + hm S
& = 8 + <
( = bend C
) = bend hm C
* or just hm one into the other.
+ = All (4) combinations of two "L" rotations which would combine into a square.
+ = All (4) "L" rotations combined together
+ = dash + cw T
+ = I + vm T
All numbers wish can be written with 4 or less letters can be combined into that number.
All numbers can be made by merging then as if in a sum (e.g 2 = 1 + 1; 3 = 1 + 1 +1, or 2+1, etc).
0 = ( + )
1 = bend dr L
2 = cw C + dash
2 = hm C + dash
2 = bend Z
3 = bend cw M
3 = bend ccw W
3 = hm C + hm C
3 = bend hm E
4 = I + I + I + dash
4 = I + I + L
5 = I + dash + hm c
5 = I + dash + ccw U
5 = cw L + hm c
5 = cw L + ccw U
6 = ( + hm C
7 = I + >
8 = O + O
8 = C + C + hm c + hm c
9 = C + )
You can rotate 9 into 6 and vice versa

hm = horizontal mirror
vm = vertical mirror
cw = clockwise
ccw = counter-clockwise
dr = 2x rotation

B = I + cw M
D = I + )
E = dash + dash + vm L
E = dash + vm F
E = "=" + L
E = "=" + vm L
F = I + cw U
H = 4 + I
H = either combination of rotated C and vertical/wm U (you only got 1 of 2).
K = Bend X
O = Bend D
R = I + I + I + ccw U
S = Bend hm 2
S = Bend dr 2
S = Bend J
U = I + J
U = I + hm J
U = J + hm J

Some heuristics to find new recipes:
- Whenever a letter which can be made with a couple component strokes (D, L, F, P, etc) is in a recipe, try and substitute those strokes in large recipe. On the other hand, if you see a I + hm c (a poor men's D), try a D instead, etc.
- Whenever you see a C (or its rotations), try also using the respective U rotation.
- Try rotating, mirroring and bending everything. The letters/symbols run the gamut from 1 unique rotation (+, #, X), to two (8, H, I), four (E, C, D) to up to eight possible ones (F, R, most digits).

By "rotation" I mean any combination of mirroring/rotating.

(The comment become to long so I will divide it into parts)

For H, you can do a rotated equal sign and rotated I.

I found you can get a C by putting L and rotated I (like -) together :)

ok i found it, just bend Y

lindseywalch what's the T recipe? i am also missing it :')