In a form_alter hook I'm trying to target the buttons to add a new paragraph but can't seem to target the specific buttons. The buttons are multiple entity references with unlimited cardinality, but for my use case I would like for once one entity is chosen, only that entity can be chosen again in the repeater, which is why I'm trying to disable the other buttons. I want to allow unlimited cardinality but only one paragraph type to be chosen at a time. This works to unset the entire row of buttons...
$form['field_select_card_type']['widget']['add_more']
But this does not work to target the specific button...
$form['field_select_card_type']['widget']['add_more']['add_more_button_grey_card_w_image']
Any help or suggestions?