Can I Change the Display Order Of "Related Apps & Spaces" Items in the Space?

You cannot change the display order of "Related Apps & Spaces" items in the space.
If you add apps and spaces in "Related Apps & Spaces", they will be listed in the following order.

1. Created datetime of the apps (in descending order)
2. Updated datetime of the spaces (in descending order)

As an alternative, in the body text of the space and thread, you can add the links of the apps in the desired order or paste the related apps.
Consider using these methods to organize information of related apps and spaces.