Who (which code) is responsible how open file dialogues appear in Ubuntu applications

Some applications (e.g. GIMP) seem to order directories first in their the File>Open, File>Save or any other file related dialogue.

Some other applications (e.g. LibreOffice) don't sort directories first. LibreOffice does not even sort out files it can not deal with in the File>Open dialogue.

For storing files, it might be desirable to also see file names belonging to other applications, e.g. to use one of them as a template for a file to be stored by modifying an existing file name (for example, if a LO file logically belongs to some context with files names following a certain pattern representing this logical context). But in a file store dialogue from e.g. LO, I would prefer to see the non-LO files names in some other colour, e.g. medium grey instead of black.

Further the formatting of the date column in file-related dialogues has the nasty file date representation: Today/Yesterday/name of a weekday or a local representation of the date for files changed more than a week ago. I dislike this particular formatting of dates. I would prefer to have ISO-8601 formatting of file dates everywhere in file related dialogues. Fortunately Thunar has something to let it always use ISO-8601 formatting. Unfortunately this is not the default setting of Thunar in a newly installed system!

Also I would prefer, if directories were more easily discernible from files, in addition to being all sorted to the top. I would prefer it, if the textual part for them uses another colour than for files (e.g. blue for directories instead of black for files ) or if at least the symbols if directories have an easily discernible colour.

Under Windows, all file-related dialogues seem to be just some other incarnation of the Windows file explorer. The good thing about that is,

• that one might easily correct a mistyped filename which one encounters in an open or save a file dialogue - even if the file name to be corrected is not the one of the file to be loaded or saved.
• One also can use the context menu functions, e.g. copy a file location to the clipboard in order to use that in some other context or program.
• One can use search patterns during the open/save file dialogues: during typing, the displayed set to be selected from narrows according to what has been typed. The search also can be made to extend from the current directory down to its subdirectories, which is a very powerful thing which I miss under Ubuntu.

So my question is:

• Who is responsible for the file-related dialogues of GUI programs?
• Is this one (or two) central instance(s)? Or is the appearance of dialogues involving file operations up to each application? In the latter case, I would have to address quite some application maintainers for improvement like those given above.