On mobile, it's a pain to reach up for the filter button when you want to see a message higher up in the same branch. Filtering is more convenient than scrolling around so it might be a good idea to move it to the bottom near where the thumb rests.
I don't know if Gio has the functionality for it yet but one solution could be that a tap activates the filter and holding your finger on the button fans out and reveals copy/new conversation buttons. The filter option would need to remain in the same place but the others could spread out in an arc around the thumb or just extend vertically.
I see your point. Perhaps long-pressing the message should filter? The button could then serve as a backup for people who don't like that kind of implicit action.
Fanning the buttons is possible, but it's complex. Generally we only want the primary action to be a floating button on the bottom, and I don't know that filtering is the primary action. It bears thinking about...