Yeah, I think, there was already an FR submitted for the deleted all completed tasks at once, which will be discussed in the following issue : #318

But what if you also added an auto delete tasks? so after X time it deletes the completed tasks from the note?

Now, coming to this specific feature. Then, setting a timer is a very complicated and sometimes dangerous functionality to implement inside a plugin. Because, Obsidian can close anytime, or the plugin can be deleted any time, so this timer can become sometimes an issue. So, it will be better if I dont deal with timers in this plugin.

But, as we know, Tasks plugin has a nice property, called on-completion (🏁 delete), so user can set this property to the tasks which they want to be deleted, after they mark them as complete. Here, I can do one thing, instead of directly deleting them, I can put them inside archive note, so user can see it later at any point in time and all their history will be saved. Also, I do understand that, at present, its not possible to set this properties from the Edit Task Modal. So, ill going to implement this things. (Thank you for creating this issue, I at least remember these things were pending) :

• Implement a way to give other properties such as on-completion, etc through the Add or Edit Task Modal.
• For the on-completion property, give a setting, whether user want to put the auto-deleted tasks inside the archive note, or permanently delete them, like how it works now.

Now, let me give a sneak peek at one very interesting feature coming in the next release. So, as we know, giving so many properties usual bloats the the tasks. So, I have implemented a feature, so user can hide a specific properties from task line, in both Reading mode and Live Editor. And they will be only visible on hovered. This will reduce a lot of visual noise and distraction while reading the notes. So, now it wont be that much of resistance to give the on-completion property to the task which user wants to get deleted after marking them as complete. So, I think this trick will do the feature you have request, atleast for now, later a better feature can be implemented.

See the GIF below :

I am moving this issue to discussions. Since a similar request already exists in #318 and the on-completion property is also supported now.