First, the 93646 adapter is not for and EdgeHD scope. It's for conventional SCTs. It's the wrong length and width.
Celestron sells one for the 9.25" EdgeHD, and you could use that adapter with a T-ring for your 600D. (https://www.celestro...dgehd-925-11-14) The larger adapter seems to have a wider (and longer) body than the older one you have. That girth might prevent vignetting that the smaller adapter might produce.
The problem comes when you want to squeeze your filter into the light path. The adapter for 9.25 and larger EdgeHDs seems fixed-length. (The one for 8" EdgeHDs has two lengths.) So your filter would thread onto the adapter and the camera onto the filter, but the sensor would be too far for sharp corners.
If the adapter (can't find a manual for it) has some interior 2" threads, it could hold the filter inside the adapter with no cost in spacing, but that seems unlikely. And even if you switched to a t-threaded filter or an SCT-threaded filter, you'd face the same complications with the reducer/adapter/camera spacing.
The radical option for perfect spacing is to build your own adapter from scratch using parts. Start from the back of the scope with an SCT-48mm adapter, a 48mm extension (length TBD), the filter, a 48mm-t-mount adapter, your t-ring and your camera. You'd need to calculate the extension length to leave your sensor at the right distance from the reducer. (There are some variable 48mm extensions so you have some fudge spacing for other filter depths.) But those bits start adding a lot to the cost if you don't have a few to start out with.
...Celestron 9.25-inch Edge HD.
I've got the #93646 T-adapter, #94295 0.7x Reducer, and a Canon 600D....