First of all, thank you for the help and advice.
I use just already a table of contents, this note is called "project overview", in each project notebook is such a note and then refers in the respective notebook to all important notes in it.
if i understand it correctly, i should create a superordinate table of contents to include all projects and pin it to the home page. this would be a solution, but the overview is rather lost due to the amount of projects/notebooks and then i would have to maintain this note constantly, which is too cumbersome for me. In a few cases where only a few important is linked to I can imagine it, but for this case because I have described unfortunately not.
The idea with the saved search helps me there rather.
Thank you, I'll try it with that.
but just to understand, it would be pleasant for me to jump into a notebook independently of the search help.
because i often have to switch back and forth between projects and then it would be great if this "reference and overview" (table of contents) note, no matter what order the notes are sorted in, is at the top because i have given this note this property.