Sorry if its an obvious question - the new folder structure, are all the less files with the underscores now the ones I should add custom styles to as opposed to the old app.less?
If you look at Gruntfile.js you should see that main.less is the only source file Grunt compiles LESS from (along with any @import rules contained within it).
In theory you can add custom styles directly to main.less or use the default file/dir structure via the files you see imported inside main.less, it’s completely up to you.
thanks for the input, makes sense. I have been away and then done nothing for two weeks afterward, I have practically forgotten how to do everything!