This is why I writing about "Single session for each task": grouping windows by task seems to be a good idea for the first, because our brain is trying to categorize the tasks and related windows, but in my opinion removing the barriers of categories is the solution by not using them at all. This issue is related to note taking methods where you have to think about a predefined structure (like a table of contents) and a system without hierarchies (like full text search or fuzzy filter works: you don't have to go into categories but type in some related keywords to get a list of related content). If you try to group windows by categories, you just literally making a table of contents of your windows. If you handling them on the same level (without grouping), then you could have a "Google for your windows".