I'm rendering an R Markdown with parameters with the rmarkdown package' render function.
rmarkdown::render("file.Rmd", params = "ask")
It opens my default browser (Chrome) asking for the parameter input. I want it to open not in my default browser, but in the viewer pane. Or, alternatively in a different browser, like IE.
I think you are using RStudio. So go to Tools -> Global Options -> R Markdown.
In the shown dropdown menue you can change to viewer pane.
Follow the instruction described by @J_F and click the Knit to HTML button. Preview will be displayed in the viewer pane. https://rmarkdown.rstudio.com/articles_integration.html
You can preview your file by using the shortcut shift + ctrl + k on rmarkdown::render("file.Rmd", params = "ask") (or shift + command + k for Mac).
EDIT: This will work if you change output preview to viewer pane in Global Options -> R Markdown do as described by @J_F
EDIT 2: Here is an image of the shortcut working in an .R document:
Download RStudio Preview version. This version will enable you to preview your R Markdown in the viewer pane.
I think the reason why you can't see it in your viewer pane is that you didn't choose the Knit to HTML. If you have already chosen the Knit to Pdf that will stay as a default so go to Knit and choose the Knit to HTML while making sure your preview is in Viewer Pane