Slowly losing coolant

Just to confirm, you are using a borescope to look in the engine and are seeing coolant at the top of the chamber?

If so, you can try the head gasket sealer but I have never had any luck with it once the gasket is already leaking. They seem to work better at catching and plugging small leaks but not once you notice loosing coolant.

Here is a guide that goes through a head gasket test just to confirm this. However, the only proper fix that I have experience with is replacing the head gasket. Again, you can give it a shot but I would not be overly optimistic. Lastly, just because the oil and coolant have not mixed yet doesn't mean it is not a head gasket. The leak may be small enough that it is only leaking into the cylinder and it is getting put out through the exhaust. Is it smoking at all?

https://www.2carpros.com/articles/head-gasket-blown-test

Let me know if you need more info and we can go from there. Thanks

If I can give my two cents. here is a video that shows how blue devil head gasket sealer works:

https://youtu.be/Xi41RFMP8Ow

Let us know how it goes.

If you confirm a head gasket I attached the process to replace the gasket. It is pretty lengthy but it is all there if you would like to perform the repair yourself. Thanks