MrNiosy

Thank you!

Regarding Things 3: I simply do not have the skills to put together that script by myself. All I can try is to copy and paste some lines, cross my fingers and hope it'll work just as expected. Maybe I should find some resources to learn apple script from scratch...

With no skills at all, I just managed to implement MacSparky's script for getting the URL of a message in Apple Mail (see https://www.macsparky.com/blog/2019/02/applescript-to-link-to-apple-mail-message/)

But I failed at getting only the subject of a specific email in order to create a nice looking markdown link. Maybe you could have a look at this and share your results?

It would also be great if you could look into getting the URL of a specific project in the task manager Things 3 (see https://culturedcode.com/things/support/articles/2803573/) 

This looks promising! Could you add support for files in finder (URL-scheme file:///path/to/file.txt)