Currently the umlaut letters count as a special signs which are not allowed in the BC<>Excel connection. This is a serious problem for our customers located in countries using the aforementioned umlaut letters, because they cannot use basic functions as Edit in Excel due to this.
It is true that as a workaround they can recreate the company anew with a different name, but this can cause both confusion and dissatisfaction with the product (forcing them to essentially use a foreign to them language when theirs is supported by the Business Central). It is also labor heavy and can bring unwanted error when transfer occurs.
Ideas Administrator

Thank you for your feedback. We released this feature as part of the functionality in 2021 release wave 1.
More specifically, the fix is available as of 22nd April 2021 and is available for all supported versions of Business Central.

Please refer to the following link for more information:

Best regards,
Mike Borg Cardona
Program Manager, Microsoft