No, I'm quite sure this is possible. The possible reason why nobody has answered is that there are not many UEP users working with Aspell and need to add additional dictionaries and visiting the forums regularly. I know the structure of Aspell support for UltraEdit, but not for UEP.
For UltraEdit on Windows there is in the program directory of UltraEdit the subdirectory
GNU\aspell. In this subdirectory are 3 subdirectories:
bin contains the Aspell library file (DLL).
data contains the files with the tables for the encoding standards
dict contains the dictionary files (*.rws) as well as some text files (*.alias, *.multi) which are needed to build special dictionaries by loading 2 or more dictionaries and merge them in memory to 1 dictionary. (That's what I suppose on looking on the files.)
Into the
dict subdirectory additional dictionary files must be copied like your German dictionaries.
After doing that and starting UEP you should see the German dictionaries in
Configuration - Spell Checker - Dictionary and select the German dictionary.
Please see also the topics
How do I install Aspell dictionary in UltraEdit UE3 and
Problems with en_GB-ize dictionary.
I can't tell you a solution which definitely works because I don't use UEP. With help of free tool
Filemon from
SysInternals (Microsoft) you should be able to see how the Aspell dictionaries are handled by UEP. Just unpack the ZIP archive of Filemon into a local directory on the computer and start it. Enter in the
Filter dialog (Ctrl+L) for
Include instead of
* the word
aspell to include only disk accesses for aspell. Then start UEP, open the spell checker configuration dialog, run a spell check and look what Filemon recorded to understand the internal process.
When Filemon is not needed anymore you can uninstall this tool by deleting all Filemon files and the key
HKEY_CURRENT_USER\Software\SysInternals in the registry.