This plugin adds a button to the editor toolbar that, when pressed, inserts the current date into the editor.
Install by searching for 'Insert Date' in Joplin Preferences -> Plugins.
As described in this forum post, most of the time I use the existing 'Insert Date Time' button, I dont need the exact timestamp, and it is overkill. This plugin addresses that.
Just to add I installed this plugin and see the same issue, correct icon in markdown editor, but a settings (cog) icon in the rich text editor. Please can this be corrected as it is a plug I hope to use every day! Thanks