The time it takes to load the hierarchy and then actually scroll to locate the items to select is significant and challenging to select the correct ones when a space contains hundreds if not thousand(s) of pages (e.g. our knowledgebase).

When a user selects a custom export, please do not auto select everything and auto expand the entire hierarchy. Allow a user to navigate the tree just like they would when in Confluence. Expand where needed - they may just need to select a few parent pages - or, if they need child pages, they are more apt to easily locate and select the correct ones when navigating the tree as they would in the UI.

It should also take significant less time if you are not loading the entire tree - load only until selected.

We use the space export often to print topics, chapters, guides since there is:
1) No method to print a selected page tree
2) The page export doesn't include the header page, copyright statement pages, toc, etc.