It is quite easy to add a tag within the file-browser (Details->Hamburger-Menu → Tags) - I really would like to see this within Photos!
It is not even possible to see the tags within the sidebar although I can select photos by tags in the left menu…
My photos already include tags (within exif-data) that are viewable even in the windows explorer - will there be an automated function that adds these tags in the near future?
You might know or not that you have posted rot the development forum. From your writing, I guess you are more of a user that wants to provide feedback and a feature request. I will flag your post for moving into the right category.
If you are willing to work into stuff and implement things yourself, you are happily welcome here! Just give a short comment then.
No problem, moved to Photos so it is easy for others to find and discuss. Cheers.