Is it possible to create a speedrun category for completing all tasks in slumber dojo in one run?

My suggestion would be that the tasks must be completed in sequence: first the first task, then the second, and so on, ending with the last one.

Time starts when selecting the first task end ends when the in-game timer stops after killing the endboss.

yeah that seems like it would be fun, like KFRRTA in smo or all KO arenas in smbw

I like this idea. I think going sequentially is good, but I would change the timing method to a sum of all times rather than using the RTA of a session on its own. My reasoning being - this category is focused on the dreams and not the dialogue in-between them. I would rethink this if there were some strategy involved where you need to enter the equipment menu to customize things during the run, but I haven't looked that far ahead.

The starting conditions of this run would be a little strange. Main quest must be finished before the run begins, so the start conditions are not normalized at all. I'm interested to try it out and experiment but that's a lot of work