>> as mentioned, I have Windows 7 and NetRunner; I want to add Trinity. I like Hare's exegnu version.
exegnu is what I needed to know.

>>however, I guess I can install Debian Live with uefi support. then load Trinity on top of it!
I think you need to find out if Windows is installed using EFI before you do anything.

>>I will have to check if I installed Windows via uefi. NetRunner is, I'm pretty sure, using uefi.
Don't be pretty sure, be absolutely positive.

>>however, you imply that there will be problems if Windows is not under uefi. presumably I would have to boot it from the 'BIOS' instead of via grub-efi. if so, not pretty but tolerable. I don't have time right now for magic surgical operations.
If Windows is installed non efi (i.e. Legacy BIOS) and other OSs are installed EFI then the PC will default to EFI boot and Windows will not be a bootable option (I had this happen with my current motherboard)
If Windows is installed EFI other OSs installed Legacy BIOS will not be a bootable option because Windows EFI boot takes precedence (it was MSs attempt to kill off Linux from mainstream PCs)
If Windows is installed EFI and other OSs are installed EFI then Grub EFI will become the primary bootloader and should provide you with a menu that shows the EFI bootable OSs. Windows will show up in Grub EFI as long as it was installed EFI and selecting it will initiate NTbootloader and start Windows.

So be absolutely positive how your system is setup and then come back and let us know so we can, if need be, walk you through the install.

Just as an aside does exegnu support EFI installation? if it doesn't and that is what you want to use you will need to get an iso of Devuan, and do the required research to ensure Devuan is EFI compatible, to install it and then install TDE of top of that.