Hi,
Unfortunately as far as I know layout definition for word documents if quite limited... HTML and PDF have much more flexibility in that regard.
My suggestion would be you combine the table and plot as one figure, then insert it as a whole. This can be easily done with the gridExtra package. Here is an example:
library(gridExtra)
library(ggplot2)
data(iris)
myTable = tableGrob(iris[1:10,])
myPlot = ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width)) + geom_point()
grid.arrange(myTable, myPlot, nrow = 1)
This is an extreamly basic example, but you'll get the idea

There is a lot of online information on getting good
layouts and
editing tables.
Hope this helps,
PJ