I tried to make two submenus to my org-capture templates: a prefix key "t" (for TODO) and a prefix key "T" (for today's TODO). When I tried to use them, the "T" key did not appear and was not accepted. Looking more deeply, it appears that it was filtered out by a mistakenly case-folding (or at least potentially case-folding) search in org-capture. I am attaching a diff which has the two line fix for this bug.