If you want to change a keyword of multiple photos, instead of deleting the old keyword and add a new one — you can change a keyword in one step.
To change a keyword in one-step – go to Keywords panel, switch to Edit mode, right-click with a mouse on a keyword, and hit “Change keyword..” menu item to replace a keyword. The dialog appears where you can specify a new keyword. When you confirm, Phototheca starts to update all selected photos and reflect the change.
This option is available within the Info panel also. Right-click with a mouse on a keyword and use the same menu item as above.
The progress of the change will be shown with the small progress bar at the bottom. Keywords changing process is going in the background, and you can use Phototheca in a meanwhile, without waiting until the process complete.
Read more: Work with keywords | Phototheca User Guide