Step 1: Use the given line \(x+y=4\).
Let a point on the line
\[
x+y=4
\]
be \((x,y)\).
Then,
\[
y=4-x
\]
Step 2: Use distance from the line.
The distance of \((x,y)\) from
\[
4x+3y-10=0
\]
is
\[
\frac{|4x+3y-10|}{\sqrt{4^2+3^2}}
\]
Since the distance is \(1\),
\[
\frac{|4x+3y-10|}{5}=1
\]
So,
\[
|4x+3y-10|=5
\]
Substitute
\[
y=4-x
\]
\[
|4x+3(4-x)-10|=5
\]
\[
|4x+12-3x-10|=5
\]
\[
|x+2|=5
\]
Therefore,
\[
x+2=5 \quad \text{or} \quad x+2=-5
\]
So,
\[
x=3 \quad \text{or} \quad x=-7
\]
Step 3: Find the two points.
If
\[
x=3,
\]
then
\[
y=4-3=1
\]
So, one point is
\[
(3,1)
\]
If
\[
x=-7,
\]
then
\[
y=4-(-7)=11
\]
So, the other point is
\[
(-7,11)
\]
Step 4: Find the distance between the two points.
\[
d=\sqrt{(3+7)^2+(1-11)^2}
\]
\[
d=\sqrt{10^2+(-10)^2}
\]
\[
d=\sqrt{100+100}
\]
\[
d=\sqrt{200}
\]
\[
d=10\sqrt{2}
\]
Step 5: Final conclusion.
Therefore,
\[
\boxed{10\sqrt{2}}
\]