Can I add custom variables in _variables.scss file?

[Skate10]

I am creating a theme for multiple projects and I needed to add some general variable to style the loader layer of the table. I checked that there is no variable for this and the $maskBGColor is used for modal dialog and I cannot use it, because they should have different values.

Is it save to add custom variables in the _variable.scss file or should I have separate file for such custom variables? Is this file updated with the update of the Designer?

Appreciate the help! Thanks!

[cagatay.civici]

Which _variables.scss files are you referring to? Is it the one under mytheme?