yes. since obsidian is an electron app, most of the app control is html-based. but if u want to have different look for app control than the notes themselves, i suggest u give more specificity to the css snippet. for example you can have two separate snippets
to affect only the settings control
.vertical-tab-content h1,
.vertical-tab-content h2,
.vertical-tab-content h3 {
...
}
to affect only the notes
.markdown-preview-view h1,
.markdown-preview-view h2,
.markdown-preview-view h3 {
...
}
here’s screenshot to show that my h2 element is being subject slightly different css snippet, where the settings has text-align attribute