When selecting multiple notes in note list in order to perform some mass action (such as tagging, deletion, etc.) it would be helpful to see the count, i.e., how many notes have been selected.
For example, here's what it looks like in Evernote when multiple notes are selected:
vs Joplin:
Joplin does provide the note count on deletion confirmation popup, so the count is being performed, my suggestion is that it is displayed prior to pressing the delete button (or any of the other mass actions).