I saw that masks are freely movable meanwhile layers seem stuck in position and can be moved only by the arrows and are selectable only one at the time.

Layer can also be moved by dragging.

You can't select multiple layer at the same time. We never figured out to do these sort of interaction as it's quite tricky which layer does what when you have more than one.

The move tool works on a group of layer ( cool to move more than one layer ).
Not the transform tool for the moment.

Mask doesn't follow the parent layer ? mm... that's sound like an issue. I will test

The mask stay on the parent layer. At least here

True I was missing something

They do follow but the layer collapses the stack, one must reopen them clicking the triangle