Have you tried MyMood?
F-droid: https://f-droid.org/packages/com.nima.mymood/
GitHub: https://github.com/NimaKhajehpour/MyMood
- Android app: √
- Custom tags: √
- Edit previous days: √
- Mood graph: √
- Export data: √
moreDays is a little more complex, but also has mood tracking feature.
F-droid: https://f-droid.org/packages/de.wuapps.moredays/
GitLab: https://gitlab.com/wuapps/moredays
- Android app: √
- Custom tags: √
- Edit previous days: √
- Mood graph: √
- Export data: √