Hi Pavel Danilchyk,
Greetings from Syncfusion support.
We have validated your queries,
Query 1: On devices (mobile, desktop), image dialog doesn’t render properly.
Query 2: Dialog doesn't render properly on small screens. and doesn’t have the option of scrolling it.
We have validated both the reported issues and able reproduce from our end, we confirmed “Insert image dialog of rich text editor doesn't render properly and unable to scroll in the mobile view” as a defect from our end and logged a report for the same. We will validate and include the fix in Vol 4 SP1 release which is expected to be rolled out on 30th Jan 2020
You can now track the current status of the report, review the proposed resolution timeline, and contact us for any further inquiries through this link: