Sony ILME-FX3 Help Manual page 339

The registration numbers [Recall Custom hold 1] through [Recall Custom hold 3] are available only when the shooting mode is
set to P/A/S/M.
Depending on the attached lens and the status of the camera when the registered setting recall is executed, the registered
settings may not take effect.
Related Topic
Assigning frequently used functions to buttons and dials (Custom Key/Dial Set.)
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