I have adapted the GTD (Getting Things Done) system as a filesystem, and use Total Commander to manage things on my phone (and dropbox+dropsync to keep it synced between devices).

Total Commander has a nice feature, which is that you can assign specific icons to files of a particular extension, and then sort in (descending) order by that extension. This means that, choosing intelligent extension names allows you to sort in a way that puts vital, urgent, important, actionable items etc in a useful order, with nice icons to match (I have chosen a simple 'traffic light' icon-set of my own design).

This works great for me, and I have been using it for years. One nice thing about it is the freedom to adapt it as time goes on and my needs change.

My current structure is something like this:

01. Actionable Tasks
02. Awaited - Delegated Tasks
03. Personal standards and rituals
04. Recurring - Ongoing Tasks and general Goals.
05. Future Ideas and other misc resources.
06. Archived (years up to 2020)
07. My 'Yay me' folder. (see: https://lifehacker.com/keep-a-file-of-your-accomplishments-302754)
08. General Resources (travel checklists, previous addresses, vaccination record, password zipped bank details, etc)

The Actionables folder looks a bit like this:

01. Actionable Tasks
├── 2021-[01-09] <-- archive of the year, to keep things unclutterred (this could have gone into folder '06.' directly, but I tend to only move these there annually.
├── 2021 ### <-- current year. Everything in this folder are 'year-span' tasks.
│ ├── 2021-[01-09] <-- archive of the previous months.
│ ├── 2021-10 ### <-- current month. '###' serves as a visual 'currentness' marker
│ │ ├── A task which is both important and urgent (in the month span sense).vital
│ │ ├── A task which is urgent but not important.urgent
│ │ ├── A task which is important but not urgent.important
│ │ └── A normal task which should simply be done as soon as possible.asap
│ └── 2021-11 <-- tasks already scheduled for next month
└── A tasks whose span is 'life-span'. Rare to put tasks here, since they most typically represent 'goals' and ideas instead, which go into other folders.

I switch things around as it suits my mood / planning habits best. E.g. sometimes I keep 'project' folders, lumping actionables inside. Sometimes I simply 'tag' tasks (e.g. "[project1] task1.asap" ). Sometimes I date/place-tag them (e.g., "@2021-10-13 Send thing to person.scheduled", though for scheduled items I tend to also duplicate them in my phone's calendar).
The files tend to be empty most of the time, but you could also edit them as normal files to add info about a task. Typically I don't need finer resolution than month-spanned tasks, but when I do, I create a new folder (e.g. "Week 2021-10-[06-12] ###" or "Tuesday") and put things there.

Once a task is completed, I rename it and place a 'dot' in front to mark it as 'done', which also makes it a hidden file and clears it from view of current tasks (unless I click the 'show hidden files button' in Total Commander). This also helps you check when istorical tasks were completed (at the resolution in which they were created - for finer control you could modify the file's date etc).

All in all, it's a system that would work anyway, but in combination with Total Commander on my phone, it makes it very appealing to use. To me it feels almost like I have a fully customizable tasks app. (and as a bonus, total commander is simply the best android file manager I've ever used).