This is a walkthrough on how to change the "edit" context command for batch files from notepad to some other text editor
Start the program and make sure you're on the "File Association" tab. On the left where it says "Search by Extension", start typing "bat". It searches as you type, so the .bat entry will come up right away. Select the pertinant entry on the list, and the middle and right panels will update with the file type details.
For this example, the right pane is what we need, because it has the list of context menu commands ("verbs" in Windows file association jargon). The one is the default double-click verb for this file type, but we're changing the "Edit" entry, so click that. Note that the current action is to run notepad.exe, and pass the file you've clicked as the parameter (that's what the "%1" is). Click the "Edit..." button.
Here you can edit the verb text and command. In the example here, I clicked "Browse...", which opens a standard Windows Open dialog, and searched for EditPlus. This should be fine if you have that particular editor installed, otherwise, choose your preferred text editor. The path to your editor will be put into the command text box. You'll need to add "%1" to the end, so that your editor knows what file you've chosen to edit. Then click "Save".
Note that there is now a tree node for Edit. The child nodes for any verb are also Edit commands, but the highest precedence setting is the one that Windows uses in the context menu. Since our modification is the top node for Edit, it's the one that Windows will use when you right click a .bat file. Done!