I use 3 workarounds for tracking my repeated tasks that don't have specific dates in my bujo:

1. I turn them into daily habits, if possible. In this way you can get a big task done in short, manageable sessions. E.g. for reducing clutter, I have "1/1/1" and "e/d/r". These are mini-habits ("e/d/r" stands for: delete one email, remove one item from the desk, remove one item from the rest of the room space). As it usually goes with mini-habits, you get so into the task once you started it, that you usually do more than the minimum quota.
2. If these tasks should be done several times a week & I do need reminders about them, I put them on my monthly habit trackers, without dates.* I use rows instead of columns for my monthly habit trackers — the number of checkboxes in a row depends on how many times per month I want to do that particular habit. I might add the date of the habit completion, in small font, under the checkbox, when I mark it as completed. As for the overall page design, to make the whole thing more usable & neat, I group non-daily habits (i.e. the ones with short rows of checkboxes) together.
3. I schedule some tasks in the monthly log (I'm talking about that part of the monthly bujo spread where you have a column of dates). It's just that, even if the task doesn't have a specific deadline, you still can look at your weeks ahead and see what's the best day for that task. And, if needed, you can just draw arrows to reschedule the task later…

I also keep a checklist of weekly review & admin tasks in Workflowy (free account). I still change & optimize it quite often, still not happy with it, so I think it doesn't make sense to keep it in my bujo or on a sheet of notepaper for now.

As for storing a pool of one-time tasks for the week in your bujo,

• I don't have a good bujo solution for that. For now, I just (a) keep such tasks in my head (for some tasks, it works better that way, at least in my case), or (b) schedule them in my monthly log, as in #3 above, or (c) write reminders about the most important tasks of the week on a sheet of notepaper & fold it over so that it could stand on my desk, on the left from the keyboard.
• If you use the original structure of a monthly bujo spread, you could store such tasks in your monthly masterlist of tasks I guess (the right side of image #1 in this showscase of monthly logs), maybe with some indication of what week that particular sublist of tasks is for…