You don't have to worry, this software is safe, I use it myself and I wouldn't mention it otherwise. It runs without installation, does not modify anything outside its own program folder, simply saves its configuration file ("ChromeHistoryView.cfg") in its own directory and does nothing else than read Opera's "History" file, which is a simple SQLite database file.
Your history data will also not be transferred to any third parties if this is your concern.
If you had an extension installed, would you like to see it change its scope completely?
I think the best thing to do would be to end the development of the extension, if you don't want to keep it, and create a new one with new functions.
As a temporary workaround, I have unfortunately downgraded my Opera to version 54.0.2952.71, which can be downloaded from https://ftp.opera.com/pub/opera/desktop/.
I filed a bug report on this and will be waiting for it to be fixed on version 55.
New update - Opera developer 56.0.3051.0 ;-)
The change log, and the announcement.
"We have a new Opera 56 developer update for you. Our developers have been working really hard on fixing bugs, and we also have another round of improvements to share with you.
- Dark mode is now implemented in pop-ups (such as battery saver, feedback, and ad blocker).
- Fix on focus in the address field, when opening new tab.
- The paste-and-go shortcut in the enhanced address bar works again.
- Implemented dark mode favicons on the Settings page.
As usual, your feedback is really important for us, so let us know if you find anything alarming.
- Chromecast support setting is missing on Windows.
- New snap package is not released this time."