this script:

% script b55880.m
ver = version
s1 = reshape(struct(), 3, 1)
s2 = reshape(s1, 10, 1)
s3 = reshape(s1, 1, 10)

a.b = 1
a31 = reshape(a, 3, 1)

produces this:

ver =  '9.5.0.1049112 (R2018b) Update 3'

s1 =   3×1 struct array with no fields.
s2 =  10×1 struct array with no fields.
s3 =  1×10 struct array with no fields.

a =  struct with fields:
    b: 1

Error using reshape
To RESHAPE the number of elements must not change.

Error in b55880 (line 7)
a31 = reshape(a, 3, 1)

matlab has a rather surprising, I think undocumented, way to create an array of empty structs:

struct_array = reshape(struct(), 3, 1)

matlab output:

struct_array = 3x1 struct array with no fields.