Anyhoo... try this for your 3 horizontal bits.
The first and last, have "proportion" set to zero.
The middle one, which you want to fill the space, set "proportion" to 1.
That should make the outer two only as wide as the control they hold.
The first and last, have "proportion" set to zero.
The middle one, which you want to fill the space, set "proportion" to 1.
That should make the outer two only as wide as the control they hold.