Convert all occurences of a style to another style

I opened a pdf file with libreoffice and saved it as odg drawing. I am rather surpriesed by the results, except all the bold fonts became “Contour” style (white inside with black borders; see Select text->Right click->Style menu).

How do I convert all occurences of “Contour” font style in the document to “Bold” (or normal) style?

LibreOffice Draw 420m0(Build:3)
Arch Linux

This will work if the character formatting is applied at the paragraph level, but if it is applied as character styles then the built-in Find and Replace dialog will not do: the “Alternate Find and Replace” extension will be necessary.