Can I search for text in article titles across all feeds?
yes you can!:-)
You could f. e. create a folder "My feeds" in the feeds panel and drop all your feeds into it.
Afterwards you can select this folder and enter a search criteria into the search text field on top of the news panel.
If you want to find your criteria in the article you might choose the search option "Find in News".
This search will include all the news of those feeds included in the folder you created.
It would be nice to search all feeds without re-arranging everything, because that changes the indentation and messes up the display of the feeds panel.
Really? If you just create one main folder and drop your current feed structure including the folders into that nothing gets changed.