I've recently discovered ability to visually style Joplin. I use it on my Linux, Windows and Android devices and amount of this devices is getting close to 10.
It would be great help to have style sync.
The way I see it:
Plan A: "Sync as note" - create "System" tab along with "All notes", "Notebooks" and "Tags" with userstyles notebook and linux.css note in it. Let system read this note after sync and refresh style (or notify about style change to restart program).
[ All notes ] [ Notebooks > ] [ Tags > ] [ System v ] userstyles linux.css linux-alt.css windows.css android.css
[x] "Show system tab" checkbox in options. [Custom style | v ] dropbox that lists content of "System"->"userstyles" [ linux ] - say we want style for all Linux; [ linux-alt ] - if we want custom style on a widescreen workstation; [ windows ] - could be useful in some cases; [ android ] - phone has different layout so separate style would be good; [ none ] - if we don't want custom styling at all.
First allows us to show "System" tab if we want to edit styles. But doesn't show on "all other devices" where we don't need to edit anything.
Second allows to choose defined style (or none) even if system tab is not shown.
Plan B: "edit style" in Options. Embed standard editor for styles, that will put file in "developer desired" location to sync.
I guess "custom style" dropdown would be helpful too.