Using Joplin 1.7.11 under Windows, I noticed that I cannot create tags that contain upper-case letters, and cannot rename tags to contain upper-case letters.
Many people may even believe that Joplin can only handle lower-case tags, because that is all that the UI allows. However, that is not the whole story: I used Evernote before, and imported all the notes from there. I had mixed-case tags there, because I used them mostly tree-like (no native tree structure in Evernote). After the import, the tags remained mixed-case.
Is there no way in the UI, or do I overlook it? Why would you want to limit this?