Mobile Nav / Navigation as Header Padding

Hi

I am trying to set the padding for the Search icon in the navigation header which is resolutely stuck at 51px.
I think I have targeted it with css but it seems it should be changeable in the customizer. Is there a setting in the customiser to target this as my child css is getting much longer than I'd like.

What I would ideally like is to move it to the left side of the mobile viewport and then to have leading underscores in front of the icon to indicate a place for text entry:

___________ {SearchIcon}

Something like that.

I am working on a minimum viewport width of 360px for Android so the leading spaces woould probably need to be set for @media max-width 400px, @media max-width 768px and @media max-width 2000px

On the last setting I ramped up the breakpoint in the Customiser to force mobile style navigation for desktop devices. I am sceptical this is the best way to achieve this. Any comments?

Thanks
Ian