Yes, tags can be a great help. I used to combine tags with a travel category. That is, any travel would be under my travel category. Then, there would be a tag to identify the individual trip.
This worked well, except that I found that I wasn't using the information about individual trips. That is, I wasn't running reports to see how much an individual trip cost. So, I stopped adding tags to denote the specific trip.
However, I can easily imagine situations where someone would find identifying separate trips quite useful!
I have been debating whether to categorize shopping under travel expenses or general expenses. This post has helped me decide that it should not be a travel expense.
Additionally, I do something similar with my travel expenses. Except my tag looks like trip:2025_03_japan. This allows me to pivot on the trip tag to get an automatic breakdown by trip.
I do this to! My tag format is a bit different but essentially the same: YYYYMMdestination (as in 202502barcelona or 202503japan for examples).
I love how useful and easy it is to see the total cost of a trip. I can also quickly see how much I have spent on a given category (such as restaurants) for any given trips.
I use a trip: tag, but with colon-separated values which lets me summarise by year or place: trip: 2024:ireland:galway hledger bal --pivot trip -2
I also have an expenses:travel account, with about a dozen subcategories. For me those trip expenses are enough of a different category that I want to see them broken out in reports.