When I select Open, Builder creates a file chooser dialog that starts out by displaying my recently-opened files. I then have to click through several levels of directories in order to reach the file I want to open. I could speed this up a little by adding a bookmark to the sidebar using nautilus, but in a big project with lots of nested directories that doesn't help much unless I create tons of bookmarks; for example, if the file I want to open is in ~/WebKit/Source/WebKit2/UIProcess/API/gtk then I have to click through six levels of folders before I can click on the file. I don't like this very much.

gedit takes a different approach: it uses gtk_file_chooser_set_current_folder() to show the directory of the file I'm currently editing when the file chooser is launched. From here, I can view recently-opened files with one click on the sidebar if need be, but I probably want to edit another file in the same directory, or in a nearby directory. This is much nicer. (Note that the documentation for GtkFileChooser explicitly recommends against what gedit is doing [1], but I think the documentation is wrong and silly: as a programmer, I don't want to open random recently-edited text files from other projects, I want to open files from the project I'm currently working on.)

(Since Builder can display multiple files at once, a somewhat different heuristic would be needed to pick the directory to show.)

[1] 
https://developer.gnome.org/gtk3/stable/GtkFileChooserDialog.html#gtkfilechooserdialog-setting-up