Thank you @roleerob!
I am willing to help with the testing, with one important caveat. I simply don't have the time to spend "in here," as much as I might like. So ... My input, accordingly, would likely be limited.
Let me tell you a secret... :) I didn't plan anything regarding to how exactly the testing should proceed and I think by giving the process a name like 'alpha testing' I was able to avoid a flood of too many willing Steemians knocking on my 'testing door' at the same time... ^^
So, I don't expect much feedback and no input would also be a good input, because then the editor seems to work. I just want to make sure that it's possible to create and edit posts with the editor using different devices and browsers. And maybe there will appear one or the other idea for taking the whole thing to the next level in future.
I will let you know in the coming days, when it's ready to be tested ;)