Hi@Edrei1,
Based on the issue that you mentioned, do you want to make the option sets allow searching within the Combo Box?
Could you please share a bit more about the scenario, do you generate the app based on the entity?
I have a test to reproduce your scene and the issue is confirmed on my side.
So far as I know, "Allow searching" is disabled by default if the Combo Box is populated with the Option set from CDS.
I also have already tested that the other data types from SharePoint and One Drive work great with the Combo Box. Even that I put a simple Table within the Items property of the Combo Box as follows, it works great with the "Allow searching".
["1","2","3"]

If you generate the app based on the entity, you could see that the SearchFields and DisplayFields are set to ["Value"] by default.
And for the SearchField, you even could not change it. It is grey and disabled.
In a word, you could not use the Searchable function for the Combo Box populated with the Option set.
If you don't have a compelling need for CDS, you might consider using SharePoint as your data source.
Currently, "Allow searching" for the Option set within the Combo Box is not supported in PowerApps.
If you would like this feature to be improved within PowerApps, please submit an idea to PowerApps Ideas Forum:
https://powerusers.microsoft.com/t5/PowerApps-Ideas/idb-p/PowerAppsIdeas
Hope it could help.
Best Regards,
Qi