Bulk editing of tasks is coming in the next version of beorg. It doesn't work quite as you've described - you'll be able to select multiple items and then choose what properties you'd like to change, and then commit to all at once.
I found out that I can do it via the task-list and saved searches.
Yes, you are correct in that you can do this via the Tasks tab and a search, I myself use beorg like this when clearing out tasks. However your original suggestion is a good one. Ideally I need to spend some time on the outliner and make some improvements to usability, this being one of them. With the current lockdown in the UK, and working at home, I've got a bit less time to spend on development (both beorg and my freelance work) at the moment due to my two young children - however I will want to make improvements to the outliner when possible as will be a big boost to the usability of beorg.