The option to enter a custom time to "steep" is labeled Anonymous. I would propose to change that to Custom or Custom Time. I think I found all instances in the source code, but I have never contributed code to KDE before, so I might need some newbie hand-holding, assuming the change is desired.
I think this makes sense. Looking forward to your patch, feel free to ask any questions :)
Patch: https://invent.kde.org/utilities/kteatime/-/merge_requests/3
Thank you for the hand-holding.