Google Sheets: Requests Handling Automation

Hi everyone!
I am new on the forum and generally in Javascript coding.

I am part of a small association that asked me to create a form to group and handle input requests from volunteers.
Needing a free and familiar solution, I chose Google Forms to collect requests. There are 3 fields to fill in: name, request (multiple choice), belonging department (multiple choice).
Editing to my use already existing guides (search "Send email from Google Sheets based on a schedule" on Google), I created a basic program with AppsScript: requests are automatically imported into a Google Sheet, then grouped in JSON format and finally sent via e-mail. Adding a time trigger, I can receive a daily summary e-mail in text. It can be also changed the design into a more pleasing HTML table.

The problem is that for my purpose isn not enough: the list of requests should always be kept compact (without empty rows), updated (for each user only the most recent request is kept and after 24h it is removed) and grouped by belonging department.
I do not have deep knowledge in Javascript coding (neither other volunteers): I can modify the source code for my needs, but I am not able to write it from scratch.
Here is the flowchart and related source code of the program.
I would be willing to work with you to solve this issue.

Regards.