I hope you can recommend me a software that will automatically display on the desktop after opening, which is equivalent to post-it notes and memos.

There is such a desktop memo software, which can be used by installing professional notes on the computer desktop:

After installing the dedicated cloud note on the computer desktop, it can be set to start automatically;

The contents of notes on post-it notes are displayed directly on the computer desktop by default and can be recorded in different ways;

Post-it notes support regular reminders. When the reminder time on the post-it note expires, the message notification will be automatically pushed.