I'm not asking for the align feature because it's not perfect enough, but I'm wondering whether there's a automated way to align 4 sets of side-by-side barplots in powerpoint without clicking and draging. Here's an example made in different software R
What you're referring to is possible in PowerPoint using the Smart-Art tools. W.r.t to the output you want, you have 2 options to choose from "Picture caption list" or "Picture Grid" (highlighted in screenshot below using double-arrow)
You can find this in the insert tab in the ribbon. Please see the sample screenshot below.