Multiple independent matrix/groups for 1d/2d effects

I want to use the WLED controller to control multiple group of lights (independent colors and effects at the same time). To keep things simple, let’s just focus on the most minimal setup:

7x addressable LED’s SK6812 (start 0, length 7)
1x on/off led (start 7)
1x on/off led (start 8)

What I want to achieve:

3x3 2d matrix with the 7 LED’s (so there are 2 “missing” LED’s)
2x1 matrix with the 2 on/off LED

What I would expect what needs to be done:

In 2d config screen:

Panel 0 with 3x3 dimension and offset 0 / 0
Panel 1 with 2x1 dimension and offset 3 / 0

In the ledmap.json file I then put in this:

{“width”:3,“height”:3,“map”: [-1,5,-1,4,6,0,3,2,1]}

Then I create a first segment with:

Start X: 0 Stop X: 3
Start Y: 0 Stop Y: 3

For the second panel I would like to create the segment like this:

Start X: 3 Stop X: 5
Start Y: 0 Stop Y: 1

But it does not let me do this when I want to save it. It automatically reverts my values to a 3x3 grid. Also the peek view always only displays 3x3.

What am I doing or understanding wrong? Is this scenario not supported? Would I need multiple controllers to achieve this? Do the 2 missing LEDs in the first panel generate some issues, shall I just wire 2 additional ones so that it’s 9 LED’s for the 3x3 grid? Is updating to v0.16-beta worth a try?