Can't save form action
I can't save the value in advanced form action that give me null.
Solution
sorry, it confused me. You were showing the edit page with the problem, now you are saying that it is working 
Forms\Components\TextInput::make('remaining_stock')
->disabled()
->suffixAction(
Action::make('addingNewStock')
->label('Add New Stock')
->icon('heroicon-m-plus')
->requiresConfirmation()
->form([
Forms\Components\TextInput::make('adding_stock')
->numeric()
->rules(['integer', 'min:0'])
])
->modalIcon('heroicon-m-plus')
->action(function (
Forms\Set $set, Get $get, array $data
): void {
$set(
'remaining_stock',
$get('remaining_stock') + $data['adding_stock']);
})
)