Currently, we have an dashboard in SharePoint 2013 Classic Mode that we want to migrate to SharePoint Online Modern Mode. One of the requirements is to retain the ability to collapse and expand the side columns (it's a 3 column layout). However, I can't seem to figure out a good way to do this in SFPx.
Modifying the CSS outside of our web part is prohibited by our internal governance, so that adds another complexity. An idea would be to develop a webpart for each section that we can use to show/hide/expand each section. Within that webpart, we could add embed all of the webparts for each section. However, I can't find anything about how to embed webparts within webparts.