Hi,
Thank you for the details, it helps a lot!
1. May I ask what phrase should I try? I have tried a few different phrases, and saw items with the same titles – but the result URLs were different. For example “tool”, I see two items named Data synchronization, but both are separate posts with the same title on different URLs.
2. Currently I can’t see a select all filter on the results page only the post type filters. I tried on our local server though, but it all seemed to work all right. If you want, you can add temporary FTP and back-end access and I will test it for you.
3. It is under reworking at the moment, but you can still make them unchecked: Under the Search Sources -> Post type search panel just delect the post types, which you want to have unchecked by default: https://i.imgur.com/9mgppj6.png
The ones that are not selected will be unchecked.
4. Unfortunately that is not possible at the moment. Synonyms are restricted to single words. This will very likely change in the future though.