This function could be added to the styles panel to check Bootstrap variables. But allowing changes there would defeat the purpose of a dedicated theme editor.
Instead of making changes there itself, it would be better to go back in to theme editor UI and update the styles
The final implementation would obviously be unique to Wappler, but it would definitely be a mix of all options out there.
I think you misunderstood me. You certainly don’t want to change any Bootstrap variables directly. You want to know which variables to add to a custom.scss file (so you can change them), so Bootstrap can be recompiled as a new theme.
Yup, misunderstood again. 
Got your point now.
Another issue reported due to body level styling - Serve side include problem
Can the CSS be copied from original page to the newly created to-be-included php file, as a workaround?
I have not used SSI yet. So if anyone who has, can come up with a solution, please contribute.