volkeu

I've also been looking for a way to do that, and found that you could save as subassembly both stock and KIS containers, KSP then will save their contents, and you can essentially copy containers with saved content. Of course, it doesn't work with mirror mode still, but you can place container mounts in mirror mode (not necessarily KIS one, it could be any part with free node, but mounts, docking ports, or nose cones works best for me), and place containers one by one as subassemblies.

SETI adaptation by @Yemo, which is part of SETI-UbM, takes care of that issue for me: https://forum.kerbalspaceprogram.com/index.php?/topic/95645-13x-seti-unmanned-before-manned-patreon/ https://github.com/Y3mo/PartOverhaulsSETI It does exactly that you need, keeping old parts and renaming overhauled parts, sometimes resizing them in the process. liquidEngine909a is LV-909a, the Terrier with integrated fuel tanks - also 1.875m. liquidEngine909_Boattail is LV-909b, still 1.25m. The only thing missing is 1.25m fuel tanks, since overhauled are sized 1.875, but TweakScale takes care of that. Also Baby Pug and Baby Valiant (0.625m versions) are very useful, since there was no reason to use 1.25m versions, and sometimes the Spark is overkill