FM / types

/usr/share/X11/xkb/types

Name	Size	Mode	Actions
basic	607	0644	edit dl rm
cancel	231	0644	edit dl rm
caps	4522	0644	edit dl rm
complete	179	0644	edit dl rm
default	178	0644	edit dl rm
extra	5437	0644	edit dl rm
iso9995	429	0644	edit dl rm
level5	8219	0644	edit dl rm
mousekeys	214	0644	edit dl rm
nokia	302	0644	edit dl rm
numpad	1955	0644	edit dl rm
pc	3353	0644	edit dl rm
README	246	0644	edit dl rm

Edit: /usr/share/X11/xkb/types/mousekeys (214B)

partial default xkb_types "default" { virtual_modifiers Alt; type "SHIFT+ALT" { modifiers = Shift+Alt; map[Shift+Alt] = Level2; level_name[Level1] = "Base"; level_name[Level2] = "Shift+Alt"; }; };