Open local html file in RStudio viewer pane

I want to preview Rmd files that are already rendered in the viewer pane. Just the final step that happens when you 'knit' a .Rmd file, but without computing everything again.

This link (https://support.rstudio.com/hc/en-us/articles/202133558-Extending-RStudio-with-the-Viewer-Pane) suggests using rstudioapi::viewer. That calls an external browser (here is google chrome). Is there an option to use RStudio viewer pane instead?