The Syncfusion MaskedTextBox component currently does not support insert-mode editing, where characters typed at the cursor position push existing characters to the right. Instead, it follows a position-based overwritten model, which is typical for masked input controls that enforce a fixed format (e.g., phone numbers, dates).
This behavior is by design, as the component is intended to maintain consistent formatting during user input.
If your use case requires insert-mode behavior, for example, editing a credit card number mid-way you might consider using a standard InputText component instead. This gives you full control over input behavior, including insert-mode editing. However, note that InputText does not include built-in masking, so you would need to implement formatting manually if required.
