Where can I find a list of defined git tags in IntelliJ IDEA (without using command line interface)?
Viewing a list of git tags has been implemented via IDEA-102284 Tags in Git Branches popup in IntelliJ IDEA v2024.2, which is slated for release in July or August of 2024. (It's in the 2024.2 EAPs as of EAP 6.) You can view tags, search for tags, and checkout by tag in the "Branches" popup (Menu: Git > Branches...)
View List of tags:
Search by Tag:
Checkout by Tag:
As @alex mentions, it is currently not possible to view tags (you can only view branches). You may want to watch and/or vote for: