Sony A6100 Help Manual page 460

Note
You can also assign shooting functions to the focus hold button on the lens. However, some lenses do not have a focus hold
button.
If you assign [Follow Custom (
movie shooting mode such as [
movie shooting mode.
If you assign [Follow Custom (
and recall the assigned function when you press the key in the playback mode.
Related Topic
Using Fn (Function) button (Function menu)
)] to a custom key using [
JPEG Quality] or [Flash Mode], the function will not be recalled when you press the key in the
/ )] to a custom key using [
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Custom Key], but the function is one that is unavailable in the
Custom Key], the camera will switch to the shooting mode