I'd like to add annotations to regions of the screen about which file / directory a region mentions.
In this way an aware terminal could let you open files by right clicking in the terminal, or change directory etc.
You could even run a program under the shell to check which files were opened and annotate areas if they are mentioned.
(The true-color sequence comes from an ITU recommended extension / future version, T.416². It would be interesting for the OP site to list which terminals support the full proposal, including CMY an CMYK specifications, as well as RGB.)
For example, there are sequences defined to change the title of the terminal window or print to a printer, but they are frequently disabled or left unsupported for security reasons.