The new “Pagination” setting introduced in ACF 6.0 helps with large repeaters by reducing the number of rows that are rendered at once, potentially avoiding browser crashes and PHP errors that might occur during repeater load or save.
However, there are a few scenarios where pagination isn’t supported. The pagination setting won’t be shown for repeater fields inside other repeaters or flexible content fields. This is something that we hope to address in a near-future release.
In addition to adding rows via the “Add Rows” button, you can also insert rows by hovering over a row and clicking the “+” / “Add Row” icon that appears in the far right of the row:
Also, pagination does not currently work inside of ACF blocks. That may change in the future, but pagination won’t be able to provide much of a performance benefit in ACF blocks due to the way that blocks store all data in the post content and DOM.