Convert it to something that Premiere will edit if fits your preference to edit in PPro .
As you say..its a proprietary codec.
Unfortunately Premiere is as finicky now as it ever has been about accepting and editing a variety of formats that other editing programs are able to handle.
Bit unfair. Premiere has worked natively with more "professional standard codecs" long before all other NLEs whilst they transcoded the proprietary and non proprietary codecs in a smoke and mirrors workflow.
What are the other finicky proprietary codecs that you would like Adobe to accomodate ?
You could ask Camatasia to be less exclusively proprietary. It's there choice to be so.. They want you to use their software.
Much like WatchTower marketing..