Allow * size in percent mode

[Harpush]

Is your feature request related to a problem? Please describe.
We have a three splitted screen which should act as:

1. 20%
2. Half of remaining place (auto)
3. Half of remaining place (auto)

Now theoretically we could say 2 and 3 are 40% but in our case the number 20 is dynamic. So we need to do (100 - x) / 2. And this scenario happens in multiple places.

Describe the solution you'd like
It could be better if in percent mode the null areas would take the remaining place distributed equally. In that way I could also save only the 1 split area size and not all three.

[Harpush]

Just adding that multiple wildcard areas are not possible as you can't know at what position they were left without binding. The linked PR implement a single wildcard support like pixel unit.