So after a long time of silence here announcing a new version in extras-devel.
0.7.1-1 is out in the wild.

I finally got it packed and uploaded to repos.
This version now keeps track of the used amount of downloaded/uploaded data traffic for each SIM separately.
Very useful if you got a limit on one (or two) of your data plan(s).

Changelog:
Version 0.7.1-1
Added possibiilty for two independent data counters for each SIM.
This functionality is auto-enabled with this version.
If you do NOT want it, execute:
rm /home/user/.config/sim-switcher/.dc_switch
To re-enable:
touch /home/user/.config/sim-switcher/.dc_switch