When Dream weaver validates the css code it reports error RBRACE expected om lines with CSS Variables (--name, var()) CSS Grid (display:grid, grid-template-columns) fr minmax()

What version of DW are you using?

Variables had always had problems for DW up until 21.6 (I haven’t updated further yet). That version seems to understand CSS Variables finally, at least under Windows 11, and admittedly on some fairly simple code.

If you could share more of your code, we might be able to find where DW is coming up short and be able to help find a workaround, or report it as a bug.

Dreamweaver Validation uses the W3C validation services below:

CSS https://jigsaw.w3.org/css-validator/

HTML https://validator.w3.org/

The difference between complied CSS for browsers & pre-processed SCSS scripting: 

https://www.geeksforgeeks.org/css/what-is-the-difference-between-css-and-scss/

Hope that helps.

Does this occur in post-processed CSS or pre-processed SCSS files?