This is a remix of the great model https://www.***********.com/thing:4778677 (which itself is loosely remixed from others, but has a much simpler digit ring design),
with the following changes:

The left side and stem are separated into two pieces.
I added a new middle piece which can be used as a separator (I personally prefer the "slim" middle piece, but I've also included a "thick" one).
The stem length can be customized via parameters in the Fusion 360 file (I included a few sample lengths).
All of these pieces can now easily be mixed and matched, so you're not stuck
with one layout (see the photo for some examples).

All necessary files (including the two versions of the digit ring) are included for your convenience.
Assembly:

Print one each of the left and right side, optionally one or more middle pieces, one stem of the correct length for your configuration, and the necessary copies of the digit ring (note that there are two versions, turning up- or downwards to count up).

The left and right end pieces fit very tightly onto the stem on purpose, but I've added some tolerance for the middle piece so it can be slid around. You should still be able to remove the ends with some gentle force, if you ever want to reconfigure your pieces.
Customization:

I've included the Fusion 360 file with all necessary parts, in case you want to
tinker more with it - like creating longer stems, or adding a logo, or adjusting the tolerance for the middle piece, etc.
Printing:

This should print quite easily with all materials, without any brim, raft or
supports. I recommend a smaller layer height for the digit rings (and possibly a
brim), but the main parts print well with 0.2 mm resolution.

Life Counter - Wound Tracker - Simple Print

0.2mm layer, 2 walls, 15% infill