how edit Reaper.ini

So I think i found it, its a note pad file. I can add the line but when I go to save it says i need to contact the owner of the file or admiun for permission. Any ideas what i need to do here?

Try running notepad as administrator.

how does this actually work? I can edit the .ini no problem, but then how do I set up the sends or whatever from tab 1 to tab 2? OK I found it.... you have to make a new hardware out on the tab 1 that is the loopback you want... then on the tab 2 you can use that as an input on the track there does seem to be a bit of a flaw in the scheme however... like this: say on tab 1 you have some sound and want to record it to tab 2 but to do that you have have tab 1 playing and then tab 2 recording so you go to tab 1 and start play then switch to tab 2 and start rec, but of course tab 1 will already be some amount of time into it's play time... right? I wonder it there could be a script or custom action to trigger tab 1 to play FROM tab 2?

Right click over the project tab and select Run background projects. With that play works simultaneously for all open project tabs.

oh great... thanks much X! actually the choice seems to be: Play stopped background project with active project that way, if tab2 is set to record inputs from tab 1, we can just got to tab 2 and hit the record button.,.. reaper is so fantastic...