It's an old topic but has relevance to the patch I posted here ->
https://sourceforge.net/p/codeblocks/tickets/182/It's a patch for Open Files List plugin implementing the preservation of previously opened (built-in) editor files per project/target basis. Some notes about the feature:
1- It doesn't save the splits but they can still be used.
2- Adds a View Menu item 'Preserve open editors' to enable/disable the feature. It can be activated/deactivated only when the workspace is empty because of implementation constraints.
3- Only built-in editors that belong to the current project can be preserved, others are left as is.
4- Last active editor and editor order are both preserved.
5- Open editor lists are saved in .layout file(s) for project(s), no extra files are created.
For you interest...