What are the different resources to announce a digression?

I'm writing a paper, and I want to add a digression to enrich the line of argumentation. I can't find good figures or resources to announce that I will introduce a digression. I came across eggresion and paradiegesis, but although related, they doesn't seem to fit my purpose.

To come back from the digression there is the resource of the "reditus ad propositum", but could someone please suggest some proper transition figures to announce the digression?

Thanks!

Naturally, it depends on what the exact digression is for.

If I were to use the digression as an illustration or example, I might use the obvious choice of

As an illustration . . .

to frame it, and return to the original line of thought once a conclusion about the example has been emphatically stated, without necessarily adding anything to state specifically that I am leaving the digression.

The one other instance where I can imagine writing in a digression is when I might want to parse out an unrelated tangent. There, I might begin with something like

On an unrelated note . . .

But this only really works if what I'm talking about something very tangential and if it doesn't really branch from the original line of thought (e.g. "On an unrelated note, there is an allusion to Kafka here, and...").

This doesn't give me a solution for what I do when I take something that obviously follows from my original line of thought, but isn't entirely relevant to the goals of my paper. In such cases, I might use the more general

As an aside . . .

(e.g. "As an aside, Engels comments in this chapter raise the issue of how division of labour is linked to freedom. This is treated in authors such as...") Possibly even the following might work:

As a diversion from the goals of this paper . . .

Whether or not I need to also specify that I'm exiting depends on how long my diversion is. If it is only a paragraph or a few sentences, then my readers will probably be able to tell that I've left it via the subject of the content that follows, without any need for clarification. If it's longer, or if it's related enough to the material that it doesn't matter, I might be perhaps well served by something like

Returning to the topic of the paper . . .

How well this works, however, perhaps depends somewhat on the exact content of the lines that follow.

I think Sherlock Holmes digressing may be a good example:

When Sherlock Holmes is digressing, I think he uses the term to talk to a reader or observer of the digression which is usually, from Sherlock's perspective, Dr Watson. When Sherlock Holmes digresses and then comes out of the digression it is usually because the observer may not be following or may confuse the observer to his main point. So he says, "Sorry Dr. Watson, I digress. Here is what we know..."

Also I think that the audience is very pivotal in a digression. If you share your digression you had better trust the people observing it. If the audience is hostile the exit from a digression can be catastrophic unless it is carefully planned out. Maybe hunting for the reason why someone attempted some method or mode that is being played out to an observer.

I think if you digressed but didn't realized until its too late you might even say, "I'm truly sorry, I must have digressed."

So may be announcement may be the following: 1. Sorry, I digress 2. Sorry, where was I, I must digress 3. Truly sorry, I must have digressed. 4. So you do understand where I'm going with this?

Good luck!?