Nested rows and columns

[Shaunson26]

Is there scope for having more complex layouts with nested columns and/or rows? I would love, for example, to have a 2 column layout, and in the first column have 1 row with 3x valueBox, and another row with 1 valueBox etc. This layout can almost be achieved with shiny fluidRow and/or fillRow .. but then the valueBox function does not seem to work independently of h3 in rmarkdown..