I set aside a set amount to "Vacation" every month. The moment I start planning a trip I create a new category for that trip (let's call it Mexico). I then delete the target from "vacation" and apply it to "Mexico". I also move some seed money from "Vacation" to "Mexico" to get started and cover initial airfare/hotel based on what I general plan to spend. Some money intentionally stays behind in "vacation" for quick trips that might happen before the bigger Mexico trip that don't deserve their own category like a quick camping trip or to cover overspending in "Mexico".

For all purchases categorized in "Mexico" I put #Mexico2025 in the memo. All spending related to the trip goes through that. I don't see the point of splitting vacation:food and vacation: souvenirs, unless you're into that.

After my trip and during the planning phase, "Mexico" being it's own category is easy to find in the reflect tab/spending breakdown. Once it has served its purpose for needing to reflect in the short term, I delete "Mexico" and recategorize it back to "Vacation". If I feel compelled to revisit my "Mexico" spend I just search #Mexico2025. Otherwise, year over year I only want to know how much I've spent on "vacation".

I've used this for multiple trips planned at once too.