Firefox Quantum 62.0 64 bits. Opensuse leap 42.3. I have crossover codeweavers installed an in one of the bottles I installed acrobat reader and the installation set it as my default PDF application. but I changed it to okular in All settings-applications-default applications and dolphin use okular to open PDF files. I also changed in firefox preferences-applications and I have all options for PDF as “previsualize in firefox” “ask” or “open with okular” and it works for most except for the button “show downloads progress”. When I download a file and the arrow icons turns blue if i click on the icon and then on the file name firefox launch adobe acrobat to open it.
I can’t find where I can change this behavior.
I’m not sure where you are clicking on an icon. However, I would guess that what you are seeing depends on a desktop setting rather than a firefox setting. I’m also not sure what desktop you are using, though I suppose that your mention of “okular” hints at KDE.