When it comes to the Insert Symbol
dialog, the behavior is implemented in this way due to the fact that once the dialog is opened, you should be able to move the caret. This covers cases when the user wants to insert symbols at different places in the document and he/she would rather not open the dialog more than once. Moreover, the behavior is the same in MS Word and at this point we are not considering a change.
As for the Custom Watermark Settings
dialog, there are no such custom requirements as watermarks are applied to the whole document with no regard to where the caret is. That said, we may reconsider the behavior of the dialog in the future, but I cannot tell if and when such a change will be made.
If you need help in implementing certain behavior of RadRichTextBox we will be glad to guide you in finding the correct approach. Please share some more details on the result you wish to achieve and your setup.
I am looking forward to your reply.
the Telerik team