Where is the documentation explaining that 'Selected Visuals' option does not retain page filters?

My sample landing page is shown below, there is a table visual displaying the Date and Sales. The slicer visual shows the Areas. There are 2 buttons pointing to bookmarks configured to perform page filter (relative date filter) for last 3 days and last 7 days respectively.

View when 'Last 3 days' button is clicked:

View when 'Last 7 days' button is clicked:

There are 2 bookmarks configured in the Bookmarks Pane:

'Last 3 days' bookmark has the following Page level filter:

'Last 7 days' bookmark has the following Page level filter:

The 2 buttons have action configured as Bookmark, as shown below.

'Last 3 days' button action:

'Last 7 days' button action:

The configuration when creating/updating the bookmark is:

Suppose the user clicks on any slicer item, then the table gets filtered showing sales for the respective area. When the user clicks on the button (Last 3 days or Last 7 days button) then the table gets filtered based on bookmark setting (page level filter).  Screenshots for this are shown above. However, the slicer selection gets reset.

The problem I am trying to solve:  Retain slicer selection across bookmarks. To do this I have found a workaround, as explained below:

1. Select all the visuals, except the slicer

2. Right click on the bookmark and choose 'Selected values'

3. Right click on the bookmark and choose 'Update'

4. Repeat the above for both Bookmarks

Now, when the user clicks on any button (3 days or 7 days), then the slicer value is retained. However the page level filter no longer maintains its bookmarked value. It appears that 'Selected Visuals' option does not retain (bookmark) page level filter.

Question 1: Please can you point me to official documentation from Microsoft where it is mentioned that the 'Selected visuals' options does not maintain page level filter.

The above problem (page level filter not getting bookmarked) can be solved with a workaround - as follows:

Note down the page level filter value for all bookmarks (for example: in a notepad file)

1. Remove the page level filter

2. Add a slicer visual with the required filter setting

3. Open the selections pane, select all visuals except the slicer visual, right click on the bookmark, ensure 'Selected visual' is check marked, click on 'Update'.

4. Repeat this for each bookmark

Using the above workaround we can have slicer values retained across bookmarks.

Question 2: The same problem as explained does not happen for filters applied at visual level (this is not explained in the example given above). Please can you point me to official documentation from Microsoft where it is mentioned that 'Selected visuals' option retains visual level filers.

Question 3: Whether there is any other alternative way to retain slicer selection across bookmarks?

Question 4: Whether there is any plan from Microsoft to implement a simpler way to retain slicer selection across bookmarks so that users don't have to use workarounds like this?