Following discussion with Writer experts, the term "Reset to Parent" is obscure and incomplete. https://community.documentfoundation.org/t/character-styles/11833/12 Although "Reset to Parent" is documented, the forum entry shows how hard is to actually reset font size and by extension, other character attributes in character style. It is suggested to add entries in the drop-down selectors of the Font tab to include "from paragraph style" (or such), which in this case, paragraph is the "parent". This bug is written as if I have to explain reset-to-parent to "John Doe" or "Aunt Martha" (fictitious characters that are not experts in Writer).
When creating character styles, it would make it easier if the font size was not available. The character style should only be a change of font, for example, changing Liberation Sans to Liberation Mono Italic. If the font used in paragraph is then changed for a different font size, the font size for the character style should also change automatically to the new size.
For any solution you need to consider, that there is an inheritance hierarchy of character styles. And only if this chain does not provide an explicit font size, the default value from the paragraph style is used. For example, paragraph style has 16pt, character style A has 24pt and a child character style B from A has 12pt. Then 'Reset to parent' in character style B will make the text formatted with style B 24pt not 16pt. There have already been a lot of discussion for a better UI, e.g. bug 88559 and bug 128960 and their duplicates. My take is, that it is not a problem of the label of the button, but of how the style dialog is designed.
This was done for bug 128469 by Seth. I would not change the label again.
Sorry if I expressed myself in confusing terms. I'm with Regina in #comment2 that the dialog should be reworked/redesigned.
(In reply to Olivier Hallot from comment #4) > I'm with Regina in #comment2 that the dialog should be reworked/redesigned. Regina's summary is to not change the label but give better feedback what exactly differs along with means to reset individual attributes. So let's resolve this ticket as NAB.