[feature] selectively delete history and flight monitoring features

It would be nice if instead of the "Clear History" button, that it had an option to selectively delete history.

My use case:
If I monitor a flight search URL, it changes often.. but I may need help remembering what price I purchased or how many points I used to reserve the flight so far. Basically the "price to beat (PTB)". I could (and have started to) put the PTB in my search's title, but it'd be nice if I could also select certain historical "changes" or ranges of changes and purge them, so that the the oldest change is shows the "price to beat".. I can quickly select that oldest change and let it compare with that one and it can be much clearer how things compare from then and now.

The reason I get into this situation is:
1) I may clone an earlier change monitor and forget to "clear history" when tweaking the search URL w/ new flight parameters
2) I may change or cancel/purchase my flight again to get a lower price and also forget to press "clear history" at the appropriate time.

Also, in general, it'd be great if this app had a more streamlined approach to flight search results price monitoring. I'm sort of "doing the best I can" with it; but it could be so much better.. part of that is G**gle Flig*ts' fault, of course; but the app could probably use some tweaks here and there to be smarter about the comparisons. such as keeping track of the price history and only alerting on drops vs changes. Maybe I just need to tweak it better... It's probably easier to do that on a single flight itinerary result; but if I am open to time ranges within a day or day ranges for travel, it quickly becomes complex.

Start by locating the existing “Clear History” button and the code that stores and displays monitor history. Review how cloned or edited flight-search monitors retain changes, then clarify the required selection and comparison behavior before implementation. Done should include an agreed way to delete selected history or ranges without losing the retained price-to-beat comparison.

Written by the indexing model from the issue text.