To rename a tag:
- Bring up the Tags screen for a page (it doesn't need to be a page tagged with the tag you want to rename)
- Tap the Edit button (top right hand corner of the screen)
- Tap the tag you want to rename
- Edit the tag name
- Tap the Save button (top right)
- The Tags screen should reappear, then tap Done
- Tap Save to exit the Tags screen
NOTE: In Trunk Notes 4.6.0 and below there is an issue with Dropbox synchronisation when renaming tags. Pages do not get updated on Dropbox with the new tags.