add post name to an existing breadcrumb

I would like parent page my posts, but “Post Parents” is not properly for me, because it can set only one parent and it have to set manually.

This is due to the fact that for pages (and other post types) a page can have only one parent, but can have many children. This is a limitation of WordPress. If you want a many to many relationship the best you can do is use a mix of taxonomy terms an posts (of any post types). Since you do not have an actual hierarchy setup, and are attempting to work outside the realm of what WordPress does, you are going to have to do a lot of stuff manually. I strongly suggest reconsidering the path you plan to follow and take some time to investigate alternate content organization structures.

So I can open posts different pages and I wolud like a properly breadcrumb which represent the current page hierarchy + the opened post. This fake breadcrumbs have only one function: user see the path and can step back any previous page.

Other than the lack of hierarchy, the other problem you have here is that you want a different type of breadcrumb trail than what Breadcrumb NavXT generates. Breadcrumb NavXT generates locational breadcrumb trails, and generally subscribes to the idea that a resource has one true location, even though there may be multiple ways of getting to it.

You are describing path breadcrumbs, which reflect the path the visitor took to an item. While Breadcrumb NavXT is sort of adding this functionality for taxonomy selection in 5.5, it probably will not get you what you want (especially if you are using all instances of the page post type and not taxonomy terms+posts).

Thank you for your detailed answer… I presume that thing a bit trickier. I cant change the hierarchy, because I have about 8 custom categories which different form paths and every post is use multiple categories… so almost impossible to make properly hierarchy.