Icon size on high resolution monitor

Hi all - a newbie here

My monitor has a resolution of 3840x2160 - this causes problems with most apps but I can scale up system-wide (I’m in Tumbleweed and KDE/plasma) and it mostly works - unless it’s a gnome app which goes its marry way without taking any notice of system settings.

And so to RT : in the File Browser the icons above and on the thumbnails are almost invisible it could be that those that are next to curves in the editing tabs are similarly afflicted, but they’re more visible.

I’ve seen that there are .css files for the interface - and one called sizes - the only thing is I don’t know which element I’m looking for to play with to try and make the icons bigger (if it were a web page, it would be easy). The alternative, I suppose - if the icons are simply displayed “as is” is to find them and double them in size.

Any ideas or solutions welcome.

We would need to know the exact specifics… versions, etc.