Hi there,
Thank you for contacting Elementor Technical support.
Upon checking your issue, we can confirm that this is a bug on our end where if you add a right margin on a flexbox container, the editor doesn’t recognize it. I have reported this to our dev team, and hopefully, they will fix it soon.
We aren’t able to provide a ETA of when it will be fixed yet. You can follow up for updates on our Changelog of Elementor to see when this issue gets resolved.
For possible workaround this could work however it requires to have container and inside it another container:
Insert a container and insert another container within. Then right-click the second container inside and insert any value at all margins at all parts and you will achieve a layout for margins across all sides.
I hope it helps.
Sorry for the inconvenience.
Have a great day!