CTRL + SHIFT + UP/DOWN remapping not working in Script Text Editor

[rogeriodec]

Godot version:
3.1 RC1

OS/device including version:
Windows 10 x64

Issue description:
I tried to remap the keyboard shortcuts "Move Up" and "Move Down" to become similar to the "Sublime Text" editor, which would respectively be Ctrl+Shift+Up and Ctrl+Shift+Down, but these combinations are not working.

Steps to reproduce:

Editor -> Editor Setting -> Shortcuts

[KoBeWi]

Move up/down CAN be remapped. Script editor just doesn't take any shortcuts that use combinations of CTRL/SHIFT and arrows. But combination CTRL + SHIFT + UP/DOWN doesn't seem to do anything normally.

[akien-mga]

Confirmed in 3.2.2 RC 3 in the script text editor.

Ctrl+Up/Ctrl+Down seem to be hardcoded to scroll the active script up/down by one line, which likely conflicts with using Shift+Ctrl+Up for other actions (here "Move Up" rebound to Shift+Ctrl+Up has this same scroll-one-line behavior).

CC @Paulb23

[akien-mga]

It's probably because TextEdit handles this directly, so combinations with Up/Down and Ctrl (Cmd+Alt on macOS) don't work:

godot/scene/gui/text_edit.cpp

Lines 3211 to 3223 in 3c9fc89

	case KEY_UP: {
	if (k->get_alt()) {
	keycode_handled = false;
	break;
	}
	#ifndef APPLE_STYLE_KEYS
	if (k->get_command()) {
	#else
	if (k->get_command() && k->get_alt()) {
	#endif
	_scroll_lines_up();
	break;
	}

[Paulb23]

Yeah looks like another case of #29490