Familiar movements make progress easier to follow. New movements can be useful when a goal, equipment change, or training plan calls for them. Give each a clear place rather than choosing between never changing anything and replacing the whole session whenever you discover another exercise.
Keep a stable foundation
Retain the key exercises that fit your program and that you can perform with appropriate control. Use consistent names and settings in the log. This provides a record you can interpret over time. Stability is valuable because it lets you see what is happening, not because every movement must remain in your program forever.
Introduce a change deliberately
Choose a new exercise for a specific purpose, learn its setup, and establish a manageable starting point. Qualified instruction is useful when the movement is unfamiliar. Do not combine learning the technique with testing the heaviest load you can move. Treat the new variation as a new record, even if it resembles an old one.
Decide whether it belongs
After giving the change a reasonable trial within your program, consider whether it fits your schedule, equipment, and ability to perform it consistently. Keep or replace it for those practical reasons. An exercise does not need to be fashionable to be useful, and discovering something new does not make the previous work meaningless.