Canon EOS R3 Advanced User's Manual page 227

Naming Custom White Balances
You can add a name (caption) to the five registered custom white balances (custom white
balance nos. 1–5).
1.
Select the custom white balance number.
2.
Select [Edit WB name].
On the [Set Custom WB] screen, select the number of the registered
custom white balance to add a name to.
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