Thanks for the update.
I'm going to look into the page and the views that you've set up and will get back to you, as soon as I can.
Just wanted to update you that I'm still working on this and will be able to share the recommendations, within the next few hours.
Thank you for waiting.
I've created some new views and a test page, to make my suggested approach more clear:
1. The test page's name is 'Test page from TS support' and you'll find the output of the 3 new views on this page:
2. The view 'parentevents-new' is set to extract Post IDs (only) for the 'Events' that we need. It has the same query filters as you added in your view 'parentevents', but the only difference is that I've structured its output to only return the comma-separated list of the post IDs.
3. The view 'Singleton Sites-new' is set to extract Post IDs (only) for the 'Sites' that we need. It has the same query filters as you added in your view 'Singleton Sites', but the only difference is that I've structured its output to only return the comma-separated list of the post IDs.
4. The view 'CombinedPlaceView-new' is the one that consolidates the IDs coming from these two views, and limits the results to only those IDs.
Please note how I've used the shortcodes of the other two views, as the shortcode attribute value for 'ids' attribute:
[wpv-view name="combinedplaceview-new" ids="[wpv-view name='parentevents-new'],[wpv-view name='singleton-sites-new']"]
And you'll find the post-ID query filter for the same in that view's 'Query Filter' section.
For the final output, you can make changes to this third view's content template, to show the list in the desired format.
You all have been so helpful. I think you give great support!