How to save as into a customized destination on macOS?
Solution 1:
By default the Save As sheet is in, for the lack of the proper term, compact view. To expand the sheet click the down arrow to the right of the Save As: text box (Export As: in Safari)
- Clicking the down arrow, the one the red arrow is pointing to, opens up the sheet showing additional controls, as in the image below
Solution 2:
I use Cmd-Shift-G often in these situations. Works in any file dialog or Finder window. This allows you to type in any custom path, or better yet, cut/copy/paste any custom path. It also keeps track of any recent paths you used.