When I define key mappings, I prefer using a modifier key with another key, because modifier key can make you so much fast if you need to press some key mapping multiple times, you only need to hold down the modifier key once and keep pressing the other key. e.g.say if I map ctrl j to cycle through opening windows. I just need to hold down ctrl once and press several time j to get to the window I want. that's just 1 * ctrl + n * j key strokes. But the <leader> key is different. <leader> key is not modifier key. So if map <leader> j to cycle through windows. I need to repeat: press <leader>, press j several times. that's n * <leader> + n * j key strokes.So is there any chance I can make the <leader> key modifier? or if you know some other way I can define my own modifier key?
Can I make  key modifier, or is there anyway I can get more custom modifier key?
key bindings
As has been said, this is not directly possible. There exists however plugins that create clever maps to achieve something similar: tinykeymap, tinymode or vim-submode