Watched and ignored videos have always been filtered out of your suggestions. That is the right default, and it is still the default — but it was also permanent, and it should not have been.

Two switches now sit in the list selector, next to the list you are choosing:

• Skip watched — on by default. Turn it off and videos you have already watched can come up again.
• Skip ignored — on by default. Turn it off and videos you dismissed with the Ignore button come back into the pool.

They belong to the list, not to your account, so one list can hide everything you have seen while another deliberately shows it. That is the useful case: a list you rewatch, like music or something you keep in the background, works better without the filter, while everything else works better with it.

Nothing is deleted when you turn a switch off, and nothing is deleted when you turn it back on. The watched and ignored marks are still recorded per video — the switch only decides whether the list pays attention to them.