Unfortunately the editor I chose (https://slate-editor.bonde.org/) is based on a deprecated version of slatejs, that played very bad with mobiles. To my dismay the current slatejs version had breaking changes. I developed myself into a corner.
I wanted to show people my prototype and usually you do that on your mobile. So I bit the bullet and rewrote the editor, which took more than double the time I expected.
I made the (Scrum) rookie mistake of not splitting up my user stories for the update. I figured the update would be 24 story points, usually my sprint velocity was about 28 story points => I thought the update would be 1 sprint max. Yeah, right :)
But at the end I am pleased with the result of the rewrite. I can use newer plugins and add new features faster now.