Extension similar to "color replace" that swaps two user defined colors. The zip file contains versions for Inkscape 0.92, 1.0, 1.1, 1.2 The underlying color extension has a regression in 1.0 and does not work on grouped objects. This has been fixed in later versions. Only tested on Windows but should work on all platforms.
Extension to mirror/flip objects along a line. The zip file contains 4 versions: for Inkscape 0.92, 1.0, 1.1, 1.2. Only tested on Windows but should work on all platforms. You need to select two objects simultaneously and then apply the extension. Select the object (shape, group, image, etc.) you want to mirror first, press "shift", and then select the mirror line (consisting of exactly 2 nodes) second. The extension can be found under "Extensions -> Modify Path -> Mirror"