How to maintain.

[HOTEC]

In general, I use the Romanic Corps for Infantry Large (LIX Corps); named corps for Infantry Small (Kempf Corps); and Numeric for Infantry Division (12. Division).

When a unit splits and merges, the original name of the unit is lost.
How could I maintain it?

[AlvaroSousa]

You can't it picks it from a list. It is too difficult to keep old names.

BTW do you know of "La Abadia del Gamer" on Discord?

This is a dedicated Spanish channel for wargames.

They have a dedicated channel for WarPlan. You can find Spanish opponents there as well.

[HOTEC]

I'm not sure there is WarPlan.

[AlvaroSousa]

I saw it before I let you know of the channel. It is under "Wargames"