Have multiple tabs support (vertical bar or horizontal bar doesn't matter).
For this, you can install the Plugin Note Tabs.
Increase font by zooming with pinch touchpad movement. Or just have better font size choices.
There was an app for Ubuntu that can add this behaviour. Just google for "ubuntu screen magnifier", it was Open Source, but that's all I can remember right now.
I'm trying to find a app for Ubuntu that has exactly same features as Joplin but different colors, and different UI.
You could try these Plugins, which provide a new theme:
Hope this helps you 