When subscribing to a channel, its videos older than current date shouldn't appear in any feed

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Checklist

• [X] I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• [X] I have read the FAQ and my problem isn't listed.
• [X] I'm aware that this is a request for NewPipe itself and that requests for adding a new service need to be made at NewPipeExtractor.
• [X] I have taken the time to fill in all the required details. I understand that the feature request will be dismissed otherwise.
• [X] This issue contains only one feature request.
• [X] I have read and understood the contribution guidelines.

Feature description

In the list of subscriptions, it should be possible to select one or more subscriptions and then choose an option "mark all videos as viewed" to mark all videos published so far in these channels as viewed.

Why do you want this feature?

Currently when adding another channel subscription your "new" tab will overflow with all the old videos from that channel and you then have to go through all those videos one by one to mark them as viewed to make them disappear from the "new" tab.

Additional information

No response