Is this somewhat related to ur other post here (How to indent the body text according to the header? - #7 by diobrando)?
I’m not sure abt select any (specific div) but u can select all divs after h3 by using the following (high level) css
.el-h3 ~ div { ... }
As per the other post, this will need contextual typography plugin (giving html layout the .el-xxx classes above).
Also note that the above applies to all items after .el-h3 (when u have more than one h3 heading). U can specify further by targeting h3 with specific title like below
.el-h3[data-heading="Journal"] ~ div { ... }
The above assumes u r targeting h3 with title “Journal”
Perhaps a demo using word processor of what u want to achieve can help others to understand and contribute to solve ur issues