In the travel / teleport menu, cities from different regions are listed together, but there’s no indication which region they belong to.
Especially for newer players (or when quickly clicking through menus), it can be confusing to remember whether a city is in Kanto, Johto, Hoenn or Sinnoh.
A small change that could help a lot would be adding the region name in brackets next to the city name.

Example:
Vermilion City (Kanto)
Olivine City (Johto)
Lilycove City (Hoenn)
Canalave City (Sinnoh)

This would make the menu clearer at a glance and reduce misclicks, without changing any functionality.
Pure QoL, but very helpful in daily use.

+1