megane-kun

As far as I understand those selectors work, using shift as the level 3 modifier is a bad idea since …

level	combination
1	key
2	SHIFT + key
3	L3 + key
4	SHIFT + L3 + key
5	L5 + key
6	L5 + SHIFT + key

I suppose customizing the keyboard layout such that SHIFT can be used as L3 modifier can be done. Otherwise, you might want to refer to /usr/share/X11/xkb/rules/evdev.lst.

Here’s the relevant part(s):

option group:option	description
lv2	Key to choose the 2nd level
lv2:lsgt_switch	The “< >” key
lv3	Key to choose the 3rd level
lv3:switch	Right Ctrl
lv3:menu_switch	Menu
lv3:win_switch	Any Win
lv3:lwin_switch	Left Win
lv3:rwin_switch	Right Win
lv3:alt_switch	Any Alt
lv3:lalt_switch	Left Alt
lv3:ralt_switch	Right Alt
lv3:ralt_switch_multikey	Right Alt; Shift+Right Alt as Compose
lv3:ralt_alt	Right Alt never chooses 3rd level
lv3:enter_switch	Enter on keypad
lv3:caps_switch	Caps Lock
lv3:caps_switch_capslock_with_ctrl	Caps Lock; Ctrl+Caps Lock for original Caps Lock action
lv3:bksl_switch	Backslash
lv3:lsgt_switch	The “< >” key
lv3:caps_switch_latch	Caps Lock; acts as onetime lock when pressed together with another 3rd-level chooser
lv3:bksl_switch_latch	Backslash; acts as onetime lock when pressed together with another 3rd level chooser
lv3:lsgt_switch_latch	The “< >” key; acts as onetime lock when pressed together with another 3rd level chooser
lv5	Key to choose the 5th level
lv5:caps_switch	Caps Lock chooses 5th level
lv5:lsgt_switch	The “< >” key chooses 5th level
lv5:ralt_switch	Right Alt chooses 5th level
lv5:menu_switch	Menu chooses 5th level
lv5:rctrl_switch	Right Ctrl chooses 5th level
lv5:lsgt_switch_lock	The “< >” key chooses 5th level and acts as a one-time lock if pressed with another 5th level chooser
lv5:ralt_switch_lock	Right Alt chooses 5th level and acts as a one-time lock if pressed with another 5th level chooser
lv5:lwin_switch_lock	Left Win chooses 5th level and acts as a one-time lock if pressed with another 5th level chooser
lv5:rwin_switch_lock	Right Win chooses 5th level and acts as a one-time lock if pressed with another 5th level chooser