I'll see how I can work around this. I use Joplin for everything, and that includes drafting webpages (they are all managed with markdown) for three different websites all of which have stacks of different CSS, that until now represented, within Joplin, rather closely to the end product. Floats, formatted tables, boxes, fonts, nearly everything. All using the same stacks of CSS. This only requires a small cut-n-pasted block of HTML at the top of such documents, slightly different for each website and slightly different for the type of page on each website. It's rather simple. The complexity is abstracted away in the CSS. Then various markdown, if need be, is wrapped in div tags (and CSS-triggering classes and ids) for floats and things. Some things like tables ... use full-on html if markdown tables just can't handle it. Yada Yada.

Plus, I just do fancy things on my own for various projects. But with those I can muddle through, it'll just be messy.

With one userstyle for everything. Oi. I suppose I can try to namespace the CSS somehow and link it all through the userstyle CSS. We'll see.

Hmm. I suppose one interim solution is to ditch Joplin as a renderer for everything that requires more than rudimentary CSS and use it only as an organizer / storage tool. Alas, Joplin renders (rendered) better than Atom (which also seems to ignore external CSS? which violates the spec) and Ghostwriter. Anyone else have a suggestion for an external editor / renderer for Linux?