Welcome to the Weekly Question Thread on c/guildwars2!
This post is dedicated to those questions that you might not think is worth making a whole post about, but sure is worth getting an answer to ;)
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There are addons but these are considered being rather a QoL features. Theres dps meter and bunch of overlays providing information while playing the game, and also an addon which helps you change mounts more easily. Game itself allows to hide some UI elements and call them upon mouse hover. But theres nothing that would mod the interface itself.
Heres the policy regarding addons: https://help.guildwars2.com/hc/en-us/articles/360013625034-Policy-Third-Party-Programs
The solution would be to take your time and get used to the UI - GW2 does lots of things differently