It’s really annoying that Renoise doesn’t remember the directory in which you saved your rendered tracks. I never save my rendered track the same place where I keep my rns. Please fix this… 
I reported about this many times before…
Renoise not only forgeting rendering path, but unpredictable change it to your “sample” path, when you switched to “sample” load mode in your discop.
And yes… It’s damn annoying
What did the devs say about this?
yeah, annoying as hell. Or better: as paradise 
Nothing… 
Maybe now they will 
yes, that’s true … the same with the render filename … it’s annoying if you like to render single columns … column after column
Maybe It-Alien will pass on message since he’s the moderator…
I don’t think this will be addressed soon: being a song property, adding it could require more tests that taktik really do not want to make now.
I thought I was the only one with such a need, so I guiltly avoided to report this before. Now I see I’m not alone
We can expect it to be added in the near future with some minor updates.
It keeps the first changed favorite in memory for the rendering.
What if you add your rendering folder as a favorite in your last song / sample / instrument preset and select this right after startup of renoise? (before selecting the rendering option or anything else)
All your renderings will end up in that folder from that moment.
This is currently the only workaround if you want to have a default rendering output folder for your running session.