this is the intended behaviour:

ctrl+click willl expand - collapse all siblings of the one that has been clicked

ctrl+alt+click will collapse just the one tree clicked, __and all of its children__ (it doesn't work reverse for expand because it's slow)

point is if I have a tree open like
```
a
    -b
         -b1
         -b2
         -b3
    -c
         -c1
              -cc1
    -d
```

clicking ctrl+alt on `a` will cause all children to collapse, so if I open `a` again, I'll see only `b,c,d` and not `b1,b2,b3,c1,cc1`