Or when you have the full path name already and want to paste it in to GtkFileChooser. It turns out this is possible, but you'd never know it from the UI.
pFileOpen->SetOptions(FOS_PICKFOLDERS | FOS_PATHMUSTEXIST | FOS_ALLOWMULTISELECT);
https://docs.microsoft.com/en-us/windows/win32/api/shobjidl_...Reference photo: https://en.wikipedia.org/wiki/File_dialog#/media/File:An_%22...
In this, a full path can be pasted in to both the top bar where it says "This PC > WINDOWS (C:)" and also into the blank "File name: | |" box.
I'm pretty sure I remember this dialogue being available since NT days. It seems fairly discoverable to me, clicking in the empty space of the current working directory path changes it to show the text path of the directory. The "File name" box offers autocomplete if you did something like "C:" as a file name, or started typing a folder name of the current working directory.