I am not sure if I use the correct terminology here, please bear with me.
I have had a year long pause in using Anki and just started again, The problem is that if I make a mistake now it adds to the existing leech/lapse count and the card might be suspended. That is not really “fair” since the reason I forgot the card isn’t that I actually forgot it if I had reviewed it as scheduled (e.g., after a couple of months) rather than after a year.
I would like the count of all my cards that causes suspension to be reset without resetting the review interval. How do I achieve that?
The leech settings are in the Deck Options preset, so if you still want to suspend leeches automatically, you can keep the old cards in the old deck (which does not change the order of reviews with the current scheduler). https://docs.ankiweb.net/leeches.html
Have you considered increasing your leech threshold by 1 or 2? They aren’t being leech-tagged to punish you – it’s just to make you aware. If you’re break means that notice is coming too soon to be useful, you can make it useful again.
Another option is to change your setting to “Tag only” – at least for a while. Realistically, any card that is reaching leech now was already on the verge of it, so there’s nothing wrong with nipping that in the bud, and starting to fix those cards now rather than later. Maybe set aside time at the end of your studying to improve any cards that reached leech that day.