Sorry about the draw tag, as the issue mainly pertains to Writer (though I also tried it with Drawing and Presentation). As explained [here](Custom gradient colors missing after saving: where are they? and see all comments) the issue is not any inability to create custom gradient colors, nor having them rendered again the same saved ODT upon reopening it, but that of saving the added custom color scheme so that, as with custom colors, it is available for future use.
Meaning for instance, if I u open up a document, and then right click in the page, and hit Page styles, and then Gradient, and then chose and modify one and hit Add to create a customized one and name it (+ hit OK), and save the document as odt (though I also tried it with Drawing and Presentation), and close and reopen it, and then repeat the steps to get to Gradient, then the scheme that you named is there for you to choose?
Since the create custom gradient schemes can vary minutely as well as greatly, then it would helpful to be able save them rather than needing to recreate them when one wants to use them on a different