[mediamonster]

I would like to be able to use modifier/control keys over terminal similarly to GUIs, e.g. use Shift+arrows to mark text, impossible on current terminals. I guess transmitting the state of all modifier keys with every keystroke would be a simple fix.

[JdeBP]

It has been possible on terminals for about three decades -- since the DEC VT220 at least.

Applications know when shift+arrow is pressed because they receive a different control sequence. Modifier keys are reported as an extra parameter in the control sequence for function keys and extended keys. Dickey xterm has been doing the same since 1999. The PuTTY changelog does not indicate when it gained this, but it has had it for years, too.

* http://invisible-island.net/xterm/xterm.log.html#xterm_94

And indeed you will find that TUI applications such as VIM and NeoVIM recognize these control sequences and can distinguish arrow from shift+arrow. See :help cursor-up and (on VIM) :help xterm-modifier-keys . (NeoVIM handles the TUI differently, is terminfo-only, and has modifier recognition always on.)

If some other application does not, then it is not the terminals that need fixing.