How could make a window always grub input focus

I do like to use keyboard instead of mouse.
And I bind “grun”(a small app for opening other applications with a name) with M+Q.However,it can not get the focus as it runs. i’d like this widget always stick on the top and grub focus when it lives.
how could this work? i’ve searched man and not find a style to achieve this. :frowning:

Style * grun Layer 8, GrabFocus

– Thomas Adam