I believe this is hard coded in org-entry-get-with-inheritance. The fastest option would be an override advice with your own function that replaces (and value " ") with (and value ""), and maybe the two other " "  with "".
 
John

-----------------------------------
Professor John Kitchin (he/him/his)
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803


On Thu, May 5, 2022 at 6:38 PM Tyler Grinn <tylergrinn@gmail.com> wrote:

I'm exporting sub-trees as pdf files for some classes I'm taking:

# -*- org-use-property-inheritance: t; -*-

* Class A
  :PROPERTIES:
  :EXPORT_FILE_NAME: support/Class A
  :END:
** Assignment 1
   :PROPERTIES:
   :EXPORT_FILE_NAME+: /assignment-1
   :END:
   Some assignment for Class A
** Assignment 2
   :PROPERTIES:
   :EXPORT_FILE_NAME+: /assignment-2
   :END:
   Some other assignment for Class A
* Class B
  :PROPERTIES
  :EXPORT_FILE_NAME: support/Class B
  :END:
** Assignment 1
   :PROPERTIES:
   :EXPORT_FILE_NAME+: /assignment-1
   :END:
   Some assignment for Class B
** Assignment 2
   :PROPERTIES:
   :EXPORT_FILE_NAME+: /assignment-2
   :END:
   Some other assignment for Class B

And this works great, except there's always a space between
'support/Class A' and '/assignment-1.pdf'. Is there any way to
concatenate the two properties rather than join them with spaces?

Best,

Tyler