1. It is currently impossible to change page's "page style" by double
clicking in side menu for example.
Intuitively (for a newish user) it seems like it should change page's "page style". Is there a philosophical (works for intended usecases) issue with it or just a technical one (not implemented)? Currently, only reliable way I found to apply the desired "page style" is to insert manual break and select desired "page style" for the next page there (which is a convoluted way and does need lots of mind numbing fiddling to get just right).
There is the principal "philosophical" idea that must be understood when working with text document: a document consists of only two things: its body text, and this text's formatting. Whatever formatting you apply, it's something that applies to (a portion of) body text.
In case of pages and their appearance, this is the greatest problem for users to realize that pages are also just a kind of formatting of part of text, not something independent. So it's very important to realize how page styles relate to text.
As with any styles, page styles are designed to minimize manual intervention. As such, page styles are not meant to require manual application to each created page, but rather to allow application to some big ranges of text, so that inside that range, the pages are created the controlled and predictable way. These ranges of text are delimited by paragraphs that include a specific property "page break with page style" in them. A text like
1 >>> a paragraph with page break with page style
2 another paragraph
3 third paragraph
4 fourth paragraph
...
24 twenty-fourth paragraph
25 >>> another paragraph with page break with page style
26 twenty-sixth paragraph
...
defines two ranges of page style application: one starting at first paragraph, and another starting at twenty-fifth one. Whenever your cursor is anywhere inside paragraphs 1 to 24, when you double-click a page style on the styles sidebar, you are working with that range, and apply the style to the first paragraph of that range (not to "current page", because "page" is not text, and as we learned, we only apply formatting to text!). A paragraph with a page break with a page style means that when this paragraph starts, a new page will be automatically created, and it will be as this page style defines it; part of that definition is "next style", which means that when following text will not fit to the page anymore, and another page must be automatically created, this "next style" will be used to define what that new page will look like. The second page's style will also have its own "next style", defining third page's look (when third page becomes necessary), and so on. (Consider different possible automatic sequences, like "cover page - title page - general pages..." or "first page - right page - left page - right page - ...", that don't require manual intervention, and do the ... (more)
English documentation
Quoting @: "So, could "next style" for pages be optional?"
What style do you think should be applied as the next style if no next style is defined?
You might better suggest to create an option like
Set this style explicitly with hard page break. Even the same page style inserted this way would break the sequence afflicted in one go by a change of the style.For me the doubleclick in the sidebar works fine. What do you mean by "currently"? Are you riding an ill horse (buggy version)?
Simply replace the term "Page style" by "Pagesequence style" in your mind. You probably will understand the working of page styles even better than.
Anyway, you can only change the page style for a sequence of layout-pages limited above and below either by start/end of document's text or by a hard pagebreak setting the new the pagestyle explicitly.
Inserting ...(more)
In addition to ebot's link, read this tutorial and this tutorial.
A general remark: styles (like any part of software) should not behave as expected or as unexpected (immediate questions: expected by who? why?), this is a wrong approach. They should behave as designed, thus (again, like with part of software), read manuals.
It does enhance the flexibility, that is why it is somewhat complicated. Complexity and flexibility go hand-by-hand.