2

1.) For desktop, copy and paste the below code snippet into your userchrome.css. Adapted from the Remoods theme notebook item scrollbar code, it provides the solution you propose.

.sidebar .list-item-container > .list-item {
  display: flex;
  border-bottom: 1px solid #FFFFFF;
  overflow-x: scroll;
}

I don't know any solutions for mobile.

2.) Prefixing search with a slash / will switch to basic search. This can be slower than full text search, but doesn't ignore non-alphabetical characters. For example: /"- [ ]" returns all notes with unchecked checkboxes. You can verify this information and more from the Searching docs page.

3.) I don't know any solutions for this.

For future reference:

Please search relevant docs for solutions before asking for support. This advice applies to Joplin features, plugin code, and any other topic.

Please describe a single specific issue per support thread. This streamlines discussion and improves discoverability for issues and solutions.