A quick fix to this is either:
1. Please permanently delete any custom icons in the trash/draft on Elementor>Custom Icons and check if this resolves the issue.
2. If you don’t have any there, just install any custom icon and then delete it right after to reset the library to its normal state. Custom Icons (Pro)
Note: This fix might affect previous custom positioning settings, if you have previously used position absolute or position fixed, please review your site. Tweak: When converting content with only a shortcode to Elementor, a shortcode widget used instead of Text Editor widget (#4616)
I think this the most amazing news for Elementor users as well as developers. This feature has been requested for a long time ?? I hope that you ll provide proper resources for developers of how to expand this feature and add own icon library.