You can achieve multiple projects deletion by using a CSV file with all the projects listed.
Instructions
To be able to delete a project you need to have Jira admin access.
Here's how you do it:
Create a CSV file with all the projects for deletion listed.
Run a command with runFromCsv like the following on CLI terminal:
--action runFromCsv --file "filename.csv" --common "--action deleteProject" --continue
Example of CSV:
project,name TEST,"Test" WIT,"Without"
After --file you should use the directory path for the CSV in question.