When you open a template in MLO on desktop,
it opens a separate file, leaving your previous one unchanged.
To access your old tasks, go to File > Reopen and select your original data file.
If you’d like to work with multiple .ml files simultaneously, you can enable this option in Tools > Options > Behavior > Allow multiple instances. This will allow each file to open in a separate window, making it easy to copy tasks between a template file and your main file if needed.