The Excel Add-in does provide support for both Key Flexfields(KFFs) and dynamic insertion where enabled.
For fields in an integrator that have been configured to allow dynamic insertion, you can enter your values directly into the field. When you are uncertain of the values, or want to select an existing combination of values, click the binoculars button to open the selector form where you can search for existing combinations.
Where a field has not been configured to support dynamic insertion you will be presented with a standard list of values that you can search in using wildcards(%).