Yes, just pop it in the fridge and use it whenever you need some. I have a bucket in my fridge where I've been dumping 'excess' starter for months. Whenever I run out of my more regularly refreshed starter I just use some of this instead. It's absolutely fine.
As for using it in a regular recipe, assuming your starter is 100% hydration (equal amounts of flour and water), just use a weighed amount to replace half that amount of flour and water (in other words, if you add 100 grams of starter, use 50 grams less each of flour and water that the recipe calls for).
Yes, just pop it in the fridge and use it whenever you need some. I have a bucket in my fridge where I've been dumping 'excess' starter for months. Whenever I run out of my more regularly refreshed starter I just use some of this instead. It's absolutely fine.
As for using it in a regular recipe, assuming your starter is 100% hydration (equal amounts of flour and water), just use a weighed amount to replace half that amount of flour and water (in other words, if you add 100 grams of starter, use 50 grams less each of flour and water that the recipe calls for).