Filter on planning screen

No it's noty possible : planning must respect WBS structure, so filtering and sorting is not possible.

Imagine WBS stucture
1. A_xx
1.1 B_xx
1.2 C_yy
2. D_yy
2.1 E_yy
2.2 F_xx
2.2.1 G_yy

Image I filter on all projets with name containing "yy"
I should show
1.2 C_yy
2. D_yy
2.1 E_yy
2.2.1 G_yy
I cannot show correct WBS structure, it's a real mess !

So yes you can select one project, then show it's whole content.
For instance select A_xx will show
1. A_xx
1.1 B_xx
1.2 C_yy
or select E_yy will show
2.2 F_xx
2.2.1 G_yy
so WBS strucutre is correct.

That's why it's not possible to filter nor sort on Gantt view.

No it's not what you get
You get complete structure from a given starting point.

What whould be a real mess is display

1 A
1.1.1.5 B
1.2 C
1.2.4.5.1 D
2.2 E
2.3 F

I would not know how to display it
A
___ B
_ C
_____ D
_ E
_ F
E and F would seem part of A, and summury bar are then impossible to draw

In fact, real structure is
A
_ X
___ X
____ X
____ X
____ X
____ X
____ B
_ C
__ X
__ X
__ X
__ X
___ X
___ X
___ X
___ X
___ X
_____ D
X
_ X
2.2 E
2.3 F