To directly answer your question without offering alternatives, as a user you can't alter the underlying code and functionality of an individual tool in Max's core code.
However, off track now and offering alternatives...If you are a coder I'm sure you can write a script to do exactly what you need. I wish I was a coder as there are a lot of things I'd be whipping up all the time.
'Shift-drag' functions like that now. It gives us new functionality because there are other tools and methods to achieve what you are after. But you mentioned you don't want to hear about options and alternatives.
The only way to get the old functionality is to go back a few Max versions and perform it there. I'm assuming the reason for changing the Old way to the New way is that there are other tools that achieve what you want to do, but you said you were either aware of or not interested in them. It makes sense that they changed it to the New way since there are other ways to do it the Old way. To me it's preferable to have those "alternate" tools plus the "New way" than to have two or three tools that all do the same old things.
I'm not trying to be dismissive of your question. I understand you want to modify Max to behave in a custom way but you can't. I think your only option is to use another tool that is specifically made to do the task to achieve the result you are after.
Lastly, it's possible that if you post to the 'Scripting' section of the Max Forums, someone might help you write the perfect Maxscript tool for you to get the functionality you want. There are some incredibally talented users in that forum.
Rob Holmes

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3ds Max (2023-2025), V-Ray 6.2, Ryzen 9 3950-X Processor, DDR 4 128MB, Gigabyte Aorus X570 Master motherboard, Sabrent Rocket NVMe 4.0 M.2 drives, NVidia RTX 4090, Space Pilot Pro, Windows 11 Pro x64, Tri-Monitor, Cintiq 13HD, Windows 11 x64
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