I decided to change the episode-prefix naming convention from 3 to 4 digits.

A fourth digit allows me to easily manage multi-part series—with only three, what would've been hard to do.

Digits, from left to right:

The first is the episode number.

The second is the "part" number—if it is zero, it's not a multipart series. As soon as it becomes one, the zero for the first part will be changed to a 1., and the second part to 2, etc.

The third is the update or tangent number.

The fourth is the update or tangent for an update or tangent.

Example: "4.3.2.1." would be the first update or tangent to the second update or tangent for the third part of the fourth episode.

Some advantages to preceding proper episode names with these digits is that if you're using a podcast player that allows you to sort episodes lexicographically / alphanumerically, doing so will automatically group episodes such that you can conveniently find all episodes and there parts / updates regardless of release date—some podcast players only allow you to sort by release date though, which in this case, the convention probably won't help you much.

Another advantage is that you can at-a-glance determine whether some episodes are multipart, etc.

Let's say "4.3.2.1." came out today and you decided to start there. By naming convention alone, you already know episode 4 has at least 3 parts,  at least 2 part-3 tangents, and at least 1 part-3-2nd-tangent parts or tangents.

Might be confusing at first, but I hope it's beneficial in the long run.