How to map space+hjkl to arrows

[kuator]

Sorry, I am noob. I'm trying to map space+hjkl to arrows, but have no idea how to do it.
What I understand is that I need to make space modifier key.
https://unix.stackexchange.com/questions/326904/make-an-ordinary-key-act-as-modifier-with-xcape-and-xkb
I found how to do it with xkb.
Now I don't know what next should I do. Should I map HPR to ISO_LEVEL_3_SHIFT? And if yes how?

As I understand these will only work with level3shift. (taken from documentation)

   key <AC06> {        [         h, H, Left            ]       };
    key <AC07> {        [         j, J, Down            ]       };
    key <AC08> {        [         k, K, Up              ]       };
    key <AC09> {        [         l, L, Right           ]       };

Again, I'm sorry, but xkb's documentation is pretty hard for newbies like me.

[khuedoan]

I use a similar set up with Right Alt remapped to AltGr and AltGr + H/J/K/L for arrow keys (xcape is for another purpose)

Haven't tested yet but you can remap your Space to AltGr (maybe in /usr/share/X11/xkb/symbols/pc? ) and edit the layout in /usr/share/X11/xkb/symbols/us

    key <AC06> {	[	  h,	H,	    Left,	   Left ] };
    key <AC07> {	[	  j,	J,	    Down,	   Down ] };
    key <AC08> {	[	  k,	K,	      Up,	     Up ] };
    key <AC09> {	[	  l,	L,	   Right,	  Right ] };

Then use xcape for Space when tapping AltGr.