If you work with separation model then you would have a Data file where you keep all data and a Graphical User Interface file with all functions, scripts and layouts. With this you can develop and do changes on your GUI-file and just change the file without having problem with data lost
In your current case you can always save all object into your Theme and save the Theme. Then import the Theme form System A to System B and if object have same name it will automatically update your style changes
A quick way to get icons from one file into another, assuming these are svg's, is to copy the buttons these icons are assigned to from System A into System B and this will automatically import the icons into System B for use elsewhere.
What I tend to do is create a button bar with multiple segments, a segment for each icon i want to transfer, then copy this object to the second file.
Hope this helps
you said style and I wonder if you meant theme. was this a custom theme with saved styles?
Yes, I meant Theme.
Yes all my icons are SVG.
Thanks for the answers.
I don't recall (cannot test) if copying a theme from one file into another (see import theme) will bring in custom SVG icons that you entered into buttons. If not, then Orlando has an excellent reply!