Hi @Pauline_Gautier
Regarding filter and group functions in List View, Timeline View, and Gantt View.
It’s a shame that these functions are not available in Timeline View at the moment.
I think the reason why they are not available is due to the drawing specifications of Timeline View compared to List View and Gantt View.
Gantt View also did not originally have a group function, but it was added later.
There is a product feedback section, so please take a look.