Hi Terminalsyzygy,
I had the same problem a long time ago and asked exactly the same question on this forum. It was before the pandemic and a guy who was a reporter visiting E3 answered my question. He gave me the same link as you to Bucket Mouse's solution and said it was easy to implement. But he did agree the solution was for advanced users only. Which is no good to a beginner, I even asked him if he could make me a guide on how to implement this solution with screen shots? He said he didn't have the time, because he was going to E3. So after that response I complained to Joe about this limitation this forum has. Because if user's of this forum won't show how the solution's are implemented with guide's/videos. Then new users of Nesmaker can easily hit this road block wall and it can stop them completely in there tracks. Because you can't even ask Joe for help either and he knows more about Nesmaker than anyone. That's why I made my original complaint to him.
So thank you for asking the same question again! I would love to know this solution too, so I will tell you everything I know so far. It's great that you are learning 6502 assemby. That is 100% the key to solving this problem, as to how to add New scripts to Nesmaker. I think you are asking? Well if you open Nesmaker and go to Scripts/Input Scripts and left click the folder. You will see 2 field's 1 called (".asm script folder") and 1 called ("visable .asm files"). In the second field you have the (<DIR> Base_4_5) link which you can go into the folders and directly click on the scripts to add them to the game. But in the first field there is a path directing Nesmaker to a folder on the users computer.
E.g. (C:\Users\Folder_Name\Another_folder_name_like_programfiles_documents_desktop_etc\Another_folder_name\Nesmaker_4_5_9\NESmaker_4_5_x\GameEngineData\Routines
(This link is going to be different for everybody. So to see the correct path, just go to Scripts/Input Scripts in Nesmaker and look at the ".asm script folder" field to see the correct path)
So if you go to this location on your computer. It will take you to where the scripts for Nesmaker are located. Like I did below: (How to do that just copy and paste the path into your search bar below on your "Toolbar" and press return. Then once the search results come up just left click on "Open File Location"). This will bring to the "Routines" folder on your computer.
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Now when the user left clicks and opens this folder you will come to this folder.
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Look Familiar?
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Left click this file again and you are bought to.
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Looking Familiar Yet?
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You sholud be getting the idea now, that the (Visible .asm files) field. Is a interface where Nesmaker is exploring the users computer. Searching for these ".asm" script files, depending which file you click on and now you know. Where these files are located on your computer. So now click on the "Game" folder you are bought to a very familiar screen.
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So these are all the file folders users, usually open up and explore to double left click on the .asm script files directly. To add them to there game, so these files are just text based files usually opened in "Notepad" and are saved ending (.asm) and written in 6502 assemby language of course. So lets's open "Mod_AdventureBase" folder then "Inputs" folder as a example.
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These are the files you get in this folder and let's open up "SelectWeapon_AdventureBase.asm" into "Notepad"
And this is what the script looks like without the Nesmaker interface, below.
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And there it is! So as long as you just write a "Notepad" document in 6502 assemby language and save it as a ".asm" (Ending in) file name and drop it into one of these folders and then select the script through Nesmaker the classic way. You can add as many original scripts to your game as you want to.
That's as much as I can help you for now. I am sorry I couldn't help you any further than that. I hope you get the answer you are looking for soon, all the best!