I didn't find an "Edit" button, so here goes again:
I tested this on a WordPress page, and it loads properly in the editor. Everything looks fine in mobile/tablet and desktop mode.
I am a little annoyed, that you cannot decide if tablet mode displays the mobile or the desktop version (at least I didn't find a setting for that). Apart from that, there's nothing I'm really missing, and I don't think there's much that you should add feature wise. Do one thing and do it well!
Picture for Reference
I did import buttons from another site, that I made in the WP-Plugin into this site, and it worked instantly. Everything was applied properly and they looked the same. I only checked call action and website URL though, because those are the ones I'm using.
I did find a few (noncritical) bugs.
At some point, the editor displayed the wrong button
When adding a new button the tool tip didn't display correctly
When trying to use the "Page" option, it doesn't load within 30 seconds, then I aborted
Performance of the site is not impacted at all, which is nice, GTMetrix reports are attached.