I suspect this is likely a feature request, and I’m not even sure you have a good way to accommodate it, given the tool set you’re using under the hood (from what little I know). But (1) I’m a user, and (2) it annoys me, so (3) complaining is what users do! 
Disclaimers out of the way, here’s the thing: I rely on the web server all the time to enter/edit notes in markdown format. Because my memory for formatting is not great, it’s helpful for me to have the source and preview panes active. Otherwise, the new stuff I enter tends to screw everything up until I get back to a macOS/iOS machine to fix whatever formatting abomination the web UI mid-wifed into the world.
My problem is this: the preview pane always scrolls to the top upon re-rendering updated content. This is just fine when I’m dealing with short notes, but as soon as my note length hits the screen length, I can no longer see what I’m typing and have to scroll manually down to see it again. A workaround whose useful lifespan is shorter than the life of the average fruit fly, unfortunately.
Is there any way to have the preview re-render position the current edit point in the middle of the preview pane? Or maybe if that’s too hard (and as a web developer myself I cringe at the prospect) just always scrolling to the bottom on re-render? Thoughts welcome.