I've already answered those same questions in the linked thread...
As I explained, the current interface to select filters may be acceptable if you activate a filter or two every other day, but is too much grinding when activating a dozen or so of filter combinations in fast succession, several times a day, like I do.
An example of my routine could be, in a single session over the Watchlist:
-show only articles,
-show articles and their talk pages,
-show only Wikipedia pages,
-show Wikipedia pages and Wikipedia talk,
-show only Wikipedia talk,
-show Draft and Draft talk.
Every day I may try these views in any order, or create different combinations of these and other filters (at any step in the above routine, I could apply over the current filter one of these: hide bots, hide minor edits, reverse the value of any filter...)
I can do all the above in the previous filters interface very fast, only with the mouse, with just one to three clicks per step, never reaching for the keyboard. With the new filters, when I de-select a filter it disappears from view, and to re-enable it I need to search for it in the long hidden list of available filters.
Every step might either add the new filter to the previous one - e.g. adding the "associated namespace", or remove the previous filter first, clearing all filters by re-loading the Watchlist page, and adding new filters.
> I assume you've discovered the ability to bookmark filter sets to the Saved Filters menu, and given it a try. Was that helpful for your use case?
Again as I explained, this partially supports my flow, but in a cumbersome and inefficient way; I'd rather stick to the old filters interface if this "pinned filters" feature is not implemented. In the previous thread you can read my explanation on all the ways the new interface is painful to use for the above case.