I've been doing some work on the webgl aspect of the Spine plugin and also doing a lot of C3 effect porting and have been looking for a good tool to help with effect / webgl debugging with Construct. I found spector.js to be very useful (The Chrome extension.)
I have had to use the 'manual' capture mode to capture Construct webgl commands to review webgl usage and effect order and results. The spector.js 'frame' capture option does not seem to work, in discussing with the spector dev, it looks like the requestAnimationFrame in C3 is not handled how they expect. Could someone from the C3 dev team please look at the last couple of comments on this issue I posted over at the spector github (they asking about why it appears to be RFA appears to be async. Note, my test case used non-worker mode - so no offscreen canvas.) I think they are willing to help on their side if they understand C3 webgl render a little better.
(With the help of spector.js as is, the Spine plugin is starting to look reasonably stable in terms of coexisting with the C3 webgl render.)