The best way to add file associations in NoteTab is through the Associations tab of the Options dialog.
1. Select View > Options from the main NoteTab menu.
2. Click on the Associations tab.
3. Enter a file extension in the "Associated File Extensions" field and then click on the "Add" button.
4. Repeat step 3 for all file extensions you want to add.
5. Click "OK" to close the Options dialog and save your changes.
Here's an example of adding the txt file extension.
If this doesn't work for you, you can associate specific file extensions with NoteTab in Windows. Please follow the instructions below:
Typically, we would suggest associating all .txt files to NoteTab, if you will be using it as your main text editor.